Classic familial adenomatous polyposis is an inherited disease where a person grows hundreds to thousands of small growths, called polyps, inside the large intestine (colon) and rectum. These polyps usually start in the teenage years or young adult life. If the polyps are not removed, many of them will slowly change into colorectal cancer. Because of this, people with classic FAP have a very high risk of bowel cancer at a young age, often before age 40 if they are not treated.
Classic familial adenomatous polyposis is a hereditary condition where a change (mutation) in the APC gene causes hundreds to thousands of small growths (polyps) in the colon and rectum, often starting in the teenage years. If the colon is not removed, the risk of colorectal cancer is almost 100% by middle age. FAP can also cause polyps and tumors in the upper gut, thyroid, bones, and soft tissues, so lifelong follow-up is essential. [1]
Classic FAP happens because of a harmful change (mutation) in a gene called APC. This gene normally works as a “brake” that stops cells from growing in an uncontrolled way. When the APC gene is damaged, the brake does not work, and polyps can grow in large numbers. This condition is passed in families in an autosomal dominant way, which means that a parent with the mutation has a 50% chance of passing it to each child.
As well as colon and rectal polyps, people with classic FAP can also get polyps and cancers in other parts of the digestive system, such as the stomach and duodenum, and sometimes tumors in other organs like the thyroid or brain. This is why lifelong monitoring and early treatment are very important in this disease.
Other names
Doctors and books may use different names for the same condition. These names usually point to the same or very closely related problems:
Familial adenomatous polyposis (FAP) – the most common short name.
Classic FAP / classical FAP – used to stress the typical form with more than 100 polyps.
APC-associated polyposis – shows that the problem comes mainly from mutations in the APC gene.
Familial polyposis coli – an older term meaning many polyps in the colon that run in families.
Adenomatous polyposis coli – another older name that also comes from the APC gene’s full name.
Sometimes related but slightly different conditions, like Gardner syndrome and Turcot syndrome, are grouped with FAP because they share APC mutations and similar colon polyps, but they also have extra tumors in other parts of the body.
Types
Even though your main topic is classic FAP, doctors often describe a small “family” of APC-related conditions around it. This helps with diagnosis and planning treatment.
Classic familial adenomatous polyposis
This type has hundreds to thousands of adenomatous polyps throughout the colon and rectum, usually starting in the teenage years. If the colon is not removed, colorectal cancer is almost certain in adult life.Profuse classic FAP
In some people, the number of polyps is extremely high, sometimes more than a few thousand, and they can appear very early in childhood. Cancer risk is very high and surgery is often needed at a younger age.Attenuated FAP (AFAP)
This is a milder form with fewer polyps (often 20–100) and later onset of cancer. It is still serious, but colon cancer tends to happen later in life compared with classic FAP.Gardner syndrome (FAP variant)
This is a form of FAP where the patient has classic colon polyps plus extra findings like bone growths (osteomas), skin cysts, and soft-tissue tumors called desmoid tumors.Turcot syndrome (APC-related subtype)
Some people with APC mutations have colon polyps plus certain brain tumors, especially medulloblastoma. This pattern is often called Turcot syndrome and is considered another variant of APC-associated polyposis.Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS)
This rare form involves dense polyps in the upper part of the stomach and is also linked to certain APC mutations. It is usually discussed together with FAP in modern guidelines.
Causes of classic familial adenomatous polyposis
Here, “causes” means both the main gene problem and factors that can change when and how the disease shows in each person.
APC gene mutation (main cause)
The key cause of classic FAP is a harmful mutation in one copy of the APC gene, a tumor-suppressor gene that controls cell growth in the intestine. When this gene is damaged, many adenomatous polyps can grow.Autosomal dominant inheritance
Because only one damaged APC gene copy is enough to cause classic FAP, it passes in families in an autosomal dominant pattern. A parent with classic FAP has a 50% chance of passing the mutation to each child.De novo (new) APC mutations
In 15–30% of people, the APC mutation appears for the first time in that person, with no earlier family history. This is called a de novo mutation and happens by chance in the egg, sperm, or early embryo.APC mosaicism
Sometimes the mutation occurs after the embryo has already started dividing, so not all cells carry the mutation. This is called mosaicism. It can cause milder or unusual forms of FAP and can explain negative blood tests in some parents of affected children.Specific mutation locations in APC
Mutations in certain regions (codons) of APC are linked to the classic, severe form with many polyps and early cancer, while other mutation spots are linked to attenuated forms. This “genotype–phenotype” link influences how serious the condition is.Loss of the second APC gene copy in cells
People are born with one damaged APC gene and one normal copy. In individual colon cells, the second copy can be lost or damaged over time, which pushes those cells toward polyp formation and, later, cancer.Activation of the Wnt/β-catenin pathway
APC normally keeps the Wnt signaling pathway under control by regulating a protein called β-catenin. When APC is damaged, β-catenin builds up and “tells” cells to grow too much, helping polyps and cancers to form.Family history of FAP or early colon cancer
A strong family history of multiple colon polyps or early colorectal cancer is a cause in the sense that it signals an inherited APC mutation shared by several relatives.Modifier genes and background genetics
Other genes, not just APC, can slightly increase or decrease the number of polyps, the age of onset, and the risk of extra-intestinal tumors. These genes do not cause FAP alone but can modify how severe it becomes.Hormonal influences
Hormones and growth factors in adolescence and early adult life may encourage faster cell turnover in the colon, helping polyps to appear earlier in people who already carry an APC mutation.Diet high in fat and low in fiber (modifier)
A Western-style diet that is high in animal fat and low in fiber does not cause classic FAP by itself, but it may speed up polyp growth and cancer changes in people who already have APC mutations.Chronic intestinal inflammation
Long-lasting irritation or inflammation in the bowel might increase the speed at which harmless adenomas change into cancer in FAP patients, though the exact size of this effect is still being studied.Smoking
Smoking does not create the APC mutation, but it can add extra DNA damage in colon cells, which can push polyps toward cancer faster in people with FAP.Alcohol overuse
Heavy and long-term alcohol use may increase colon cancer risk in the general population and is thought to add extra risk on top of an APC mutation in FAP.Obesity and lack of exercise
Being overweight and inactive are known risk factors for colorectal cancer in the general public and likely make the cancer risk even higher in people with classic FAP.Delayed or absent colonoscopic surveillance
When people with FAP are not monitored with regular colonoscopy and polyp removal, polyps have more time to grow and become cancer. This lack of surveillance is a strong “practical cause” of early cancer.Delayed prophylactic colectomy (colon removal)
In classic FAP, removing the colon at the right time greatly lowers cancer risk. If this surgery is delayed until many large or advanced polyps are present, cancer is more likely to appear.Lack of genetic counseling and testing in at-risk relatives
When children or siblings of a person with FAP are not tested, they may grow up with undetected disease and present late with cancer. So, missed genetic testing becomes an indirect cause of severe outcomes.Limited access to specialist care
In some regions, people cannot easily reach colonoscopy services, genetic tests, or expert surgeons. This health-system factor can cause later diagnosis and more advanced disease.Poor awareness among healthcare providers and families
If doctors and families do not recognize the pattern of early rectal bleeding, family history, and anemia, the diagnosis may be delayed. This lack of awareness does not create APC mutations but is a practical cause of late detection.
Symptoms of classic familial adenomatous polyposis
Symptoms often start in the teenage years or young adult life, but some people feel well until cancer is already present.
Rectal bleeding (blood in stool)
One of the most common signs is bright red or dark blood mixed with stool or on toilet paper. It happens because fragile polyps are easily damaged and bleed as stool passes by.Chronic anemia (low blood count)
Slow, repeated bleeding from many small polyps can cause iron-deficiency anemia. People may feel tired, weak, or short of breath because their blood carries less oxygen.Change in bowel habits
Patients may notice new constipation, diarrhea, or alternating patterns that last for weeks or months. These changes can be due to the large number of polyps and, later, to growing cancers that disturb normal movement of stool.Abdominal pain or cramps
Many polyps or a large tumor can stretch the bowel wall or cause partial blockage, leading to crampy or colicky abdominal pain. Sometimes the pain is vague and mild at first.Mucus in stool
Adenomatous polyps often produce mucus. Patients may see clear or whitish mucus mixed with stool or passed alone, especially when polyps are large or numerous.Unexplained weight loss
As cancer develops or when many polyps cause chronic blood loss and poor absorption, people may lose weight without trying. This is a warning sign that always needs medical review.Abdominal mass or fullness
Large colon cancers, desmoid tumors (soft-tissue growths), or a very polyp-laden colon can sometimes be felt as a lump or fullness in the abdomen.Symptoms of bowel obstruction
Nausea, vomiting, inability to pass stool or gas, and severe crampy pain can appear if a large tumor or tight desmoid tumor causes a blockage in the intestines. This is an emergency.Fatigue and reduced exercise capacity
Chronic anemia, poor nutrition, and cancer-related effects can make people feel exhausted, breathless with small effort, or sleepy during the day.Polyps and cancer in upper digestive tract
Some people get symptoms like upper abdominal pain, nausea, or black stools (melena) because of duodenal or gastric polyps and cancers that also bleed.Tooth and jaw problems (Gardner variant)
People with Gardner-type FAP may have extra teeth, impacted teeth, or jaw bone growths that cause discomfort or cosmetic issues.Bone and skin lumps
Osteomas (bony growths), soft-tissue tumors, and skin cysts can appear, especially in Gardner syndrome, and may bring patients to the doctor even before bowel symptoms do.Thyroid nodules
Some patients, especially young women, develop thyroid nodules or thyroid cancer. A painless neck lump or feeling something in the neck may be noticed.Liver or brain symptoms in advanced disease
If colorectal cancer spreads, people may develop symptoms like jaundice, headaches, seizures, or personality changes, depending on where the metastases grow.Completely silent early stage
Many teenagers and young adults with classic FAP have no symptoms at all. The disease may first be found on screening colonoscopy or only when cancer is already present. This is why family screening is so important.
Diagnostic tests
Physical examination tests
These tests are done by the doctor using eyes, hands, and simple tools during the clinic visit.
General physical examination and vital signs
The doctor checks weight, height, blood pressure, heart rate, and general appearance. Pale skin, low weight, and signs of poor nutrition can suggest long-standing bleeding or cancer from FAP.Abdominal inspection and palpation
The doctor gently presses on different parts of the abdomen to look for pain, masses, or swelling. A large colon tumor or desmoid tumor can sometimes be felt as a firm lump or may cause localized tenderness.Rectal inspection
Visual examination of the anal area can show external bleeding, prolapsed polyps, or other signs of disease. While many FAP polyps are higher up, this step is still important as a first check.Growth and development check in children and teens
For younger patients at risk, doctors follow growth charts and puberty markers. Delayed growth, weight loss, or anemia can be indirect clues that bowel disease like FAP is present.
Manual tests
These tests are done mainly by hand and focus on feeling organs and structures.
Digital rectal examination (DRE)
The doctor gently inserts a gloved, lubricated finger into the rectum to feel for masses, large polyps, and tenderness. In classic FAP, multiple small polyps or a low rectal tumor may be felt, which prompts urgent colonoscopy.Deep abdominal palpation for masses
Using deeper pressure, the doctor feels organs such as the colon, liver, and spleen. A firm, irregular mass may suggest advanced colorectal cancer or a large desmoid tumor, both of which are linked with FAP.Manual lymph node examination
The doctor feels lymph nodes in the neck, armpits, and groin. Enlarged nodes can be a sign that cancer has spread, although infections can also cause swelling. This exam helps stage the disease.
Lab and pathological tests
These tests look at blood, stool, and tissue under the microscope.
Complete blood count (CBC)
A CBC measures red blood cells, white blood cells, and platelets. In FAP, chronic blood loss from polyps often leads to low hemoglobin and small, pale red cells, which shows iron-deficiency anemia.Iron studies
Blood tests for ferritin, iron, and total iron-binding capacity help confirm iron-deficiency anemia. Low ferritin and iron with high binding capacity support the idea of chronic blood loss from bowel polyps or cancer.Fecal occult blood test (FOBT) or fecal immunochemical test (FIT)
These stool tests look for tiny amounts of hidden blood that cannot be seen with the eye. In people with many polyps, these tests are often positive and can be a first clue that something is wrong.Serum chemistry and liver function tests
Blood tests that check liver enzymes, bilirubin, and proteins help detect liver metastases from colorectal cancer or side effects from treatments. Abnormal results may lead to imaging tests like ultrasound or CT.Germline APC genetic testing
This is a key test. A blood sample is used to look directly at the APC gene for harmful mutations. Finding a disease-causing variant confirms the diagnosis of APC-associated FAP and allows testing of family members.Testing for other polyposis genes (e.g., MUTYH) when needed
If APC testing is negative, or if the pattern is not typical for classic FAP, tests for MUTYH and other genes are done. This helps distinguish FAP from MUTYH-associated polyposis or Lynch syndrome.Polyp or tumor biopsy with histopathology
During colonoscopy, the doctor removes polyps or takes tissue samples. A pathologist examines them under the microscope to confirm they are adenomas and to check for high-grade changes or cancer. This is central to diagnosis and staging.Advanced tumor molecular testing
For cancers, extra tests may be done on tumor tissue to look at APC mutations, β-catenin, and other markers. These tests mainly help research and sometimes treatment planning, but they also support the link to APC-associated polyposis.
Electrodiagnostic tests
There is no special nerve or brain electrical test that diagnoses FAP itself, but some electrodiagnostic tests are used as part of pre-surgical and overall care.
Electrocardiogram (ECG)
An ECG records the heart’s electrical activity. It is usually done before major surgery, such as colectomy, to make sure the heart is safe for anesthesia. This is not specific to FAP but is part of safe care for these patients.Electromyography (EMG) or nerve conduction studies when needed
In rare situations, if patients receive certain chemotherapy drugs or have neurological symptoms, tests of nerve and muscle electrical activity may be used. These tests do not diagnose FAP, but they help manage complications of treatment.
Imaging and endoscopic tests
These tests use cameras or imaging machines to look directly at the bowel and other organs. They are the most important tools in FAP.
Colonoscopy
Colonoscopy uses a flexible camera tube to look at the entire colon and rectum from inside. In classic FAP, colonoscopy usually shows hundreds to thousands of adenomatous polyps. It allows polyp removal, biopsy, and planning for surgery.Flexible sigmoidoscopy
This test looks at the rectum and the lower part of the colon. It is sometimes used as a first test in young people with rectal bleeding, but full colonoscopy is preferred when FAP is suspected because polyps often extend throughout the colon.Upper endoscopy (esophagogastroduodenoscopy)
A flexible camera is passed through the mouth to see the esophagus, stomach, and duodenum. People with FAP have a higher risk of duodenal and gastric polyps and cancers, so regular upper endoscopy is recommended in guidelines.Cross-sectional imaging (CT or MRI of abdomen and pelvis)
CT or MRI scans create detailed images of the abdomen and pelvis. They help detect large desmoid tumors, liver metastases, bulky colon cancers, and other complications of FAP. MRI is often preferred for repeated imaging because it avoids radiation.Ultrasound for thyroid and abdomen
Neck ultrasound checks for thyroid nodules or thyroid cancer, which are more common in FAP, especially in young women. Abdominal ultrasound can also help screen for liver metastases or large intra-abdominal masses.
Non-Pharmacological Treatments (Therapies and Strategies)
1. Genetic counselling and testing
Genetic counselling helps the family understand APC gene mutations, inheritance patterns, and cancer risk. The purpose is to identify who in the family carries the mutation so they can start screening early. The mechanism is not biological but informational: by mapping the family tree and offering APC testing, doctors can focus colonoscopy and prevention on people at highest risk and avoid unnecessary procedures for those who test negative. [1]
2. Early and regular colonoscopy
High-definition colonoscopy lets doctors see and remove many polyps before they turn into cancer. The purpose is early detection and polyp removal. The mechanism is purely mechanical: the camera shows the inner lining of the bowel, and instruments through the scope snip off polyps so they cannot grow into cancer. In classic FAP, colonoscopy usually begins in early adolescence and is repeated every 1–2 years until surgery. [2]
3. Flexible sigmoidoscopy when colonoscopy is not yet needed
In some settings, flexible sigmoidoscopy is used first, especially in very young patients, to look at the rectum and lower colon where polyps appear early. The purpose is to screen with a shorter, sometimes easier test. The mechanism is similar to colonoscopy but examines only part of the bowel; if adenomas are seen, a full colonoscopy is arranged. [3]
4. Endoscopic polypectomy
During colonoscopy or sigmoidoscopy, small polyps can be removed using snares or forceps. The purpose is to reduce polyp number and delay cancer. The mechanism is local removal: when a polyp is cut off at its base and retrieved, the abnormal cells are gone from that spot, and the tissue is checked under a microscope to assess cancer risk. [4]
5. Upper-GI endoscopy for stomach and duodenal polyps
FAP also causes polyps in the duodenum and around the ampulla. Upper-GI endoscopy uses a flexible scope passed through the mouth to inspect these areas. The purpose is to catch high-risk duodenal lesions early. The mechanism is visual grading of polyps and biopsies; results guide how often endoscopy is repeated and when surgery is needed. [5]
6. Side-viewing duodenoscopy for ampullary lesions
A side-viewing endoscope gives a better angle on the bile and pancreatic ducts, which is important in FAP because ampullary adenomas carry a higher cancer risk. The purpose is fine, detailed inspection and targeted biopsies. Mechanistically, improved visualization helps detect small, flat lesions that may be missed with standard forward-view scopes. [6]
7. Thyroid ultrasound surveillance
People with FAP have a higher risk of papillary thyroid cancer. Regular neck ultrasound can spot small nodules early. The purpose is early diagnosis and treatment of thyroid disease. The mechanism is simple imaging: sound waves create a picture of the thyroid, allowing doctors to see suspicious lumps and guide fine-needle biopsy when needed. [7]
8. Individualised timing of prophylactic colectomy
Deciding when to remove the colon is a key non-drug intervention. The purpose is to perform surgery before cancer appears but after careful planning. The mechanism is risk stratification: doctors look at polyp number, size, dysplasia, family history, and patient age to choose the safest time and the most suitable type of colectomy rather than using a fixed age for everyone. [8]
9. Lifestyle counselling: stop smoking
Smoking increases overall cancer risk and can worsen surgical outcomes. The purpose of counselling is to support complete smoking cessation. The mechanism involves behavioural change techniques and nicotine replacement where needed, reducing inflammation, improving blood flow, and helping tissues heal better after major abdominal surgery. [9]
10. Weight control and regular physical activity
Obesity and inactivity are associated with higher colorectal cancer risk in the general population. For FAP, they add extra burden to an already high-risk situation. The purpose of exercise and weight control is to support gut health, heart health, and recovery after surgery. Mechanistically, physical activity improves insulin sensitivity, reduces chronic inflammation, and strengthens muscles that support bowel function. [10]
11. High-fibre, plant-forward eating pattern
A diet rich in vegetables, fruits, whole grains, and legumes increases fibre and beneficial plant compounds. The purpose is to support regular bowel movements and a healthier gut microbiome. The mechanism is mainly mechanical and metabolic: fibre adds bulk to stool, shortens transit time, and gut bacteria produce protective short-chain fatty acids, which may support colon cell health. [11]
12. Limiting red and processed meat
Frequent intake of processed meat and large amounts of red meat is linked to higher colorectal cancer risk in the general population. For someone with FAP, this extra risk is undesirable. The purpose of cutting down is to remove avoidable carcinogenic exposures. Mechanistically, cooking meat at high temperature and processing with nitrites can form compounds that damage colon cell DNA. [12] [11]
13. Psychological support and counselling
Living with FAP, repeated procedures, and the knowledge of high cancer risk is emotionally heavy. The purpose of psychological support is to reduce anxiety, depression, and medical trauma. The mechanism includes talk therapy, coping skills, and sometimes family sessions, which help patients stick to long-term surveillance and feel more in control. [13]
14. Reproductive and family-planning counselling (including PGD)
Because FAP is autosomal dominant, each child has a 50% chance of inheriting the mutation. The purpose of reproductive counselling is to discuss options such as prenatal testing or pre-implantation genetic diagnosis (PGD). The mechanism is informational and ethical guidance: couples learn how assisted reproduction can select embryos without the APC mutation, if they choose that path. [14]
15. Education on red-flag symptoms
Patients and families are taught to recognise warning signs such as rectal bleeding, persistent diarrhoea, sudden change in bowel habits, severe abdominal pain, or unexplained weight loss. The purpose is to encourage early medical review rather than waiting. The mechanism is self-monitoring: better awareness leads to earlier colonoscopy or imaging when something changes. [15]
16. Multidisciplinary specialist clinic follow-up
Care in a hereditary colorectal cancer clinic, with gastroenterologists, colorectal surgeons, geneticists, psychologists, and dietitians, improves coordination. The purpose is to create one integrated care plan. The mechanism is team-based decision-making, ensuring surveillance, surgery, and family testing are not missed and that information is consistent. [16]
17. Post-surgical pelvic floor and stoma training
After colectomy, some patients have an ileal pouch or a stoma. Teaching stoma care, pelvic floor exercises, and toileting routines is key. The purpose is to improve continence, skin health, and quality of life. The mechanism is practical training plus muscle strengthening, so patients gain confidence and avoid complications such as leakage or skin irritation. [17]
18. Pain and symptom management without overusing NSAIDs
Pain from surgery or desmoid tumours can be significant. The purpose of a structured pain plan is to control symptoms while avoiding long-term high-dose NSAIDs, which have cardiovascular and kidney risks. The mechanism may include physiotherapy, relaxation techniques, and carefully supervised medicines in short bursts only. [18]
19. Support groups and patient organisations
Connecting with other people who have FAP provides emotional support and practical tips. The purpose is to reduce isolation and improve coping. The mechanism is peer learning and shared experience: patients see real-life examples of living well after colectomy, managing fertility, and gradually returning to normal activities. [19]
20. Individualised surveillance of extra-colonic sites
FAP can affect the duodenum, stomach, thyroid, pancreas, and other organs. The purpose of personalised surveillance is to focus effort where each patient’s risk is highest. The mechanism is risk-stratified imaging and endoscopy based on polyp stage, family history, and guideline recommendations rather than a “one size fits all” plan. [20]
Drug Treatments
Very important: All medicines below are examples from research and FDA-approved colorectal cancer treatments. They must never be started or adjusted without a specialist. Some have serious risks, and some FAP-related indications have been withdrawn or are off-label.
1. Celecoxib (Celebrex)
Celecoxib is a COX-2 inhibitor NSAID that was approved to reduce the number of colorectal adenomas in FAP as an adjunct to usual care, such as endoscopy and surgery, although the specific FAP indication has since been withdrawn in some regions because of cardiovascular safety concerns. Typical study doses were 400 mg twice daily in adults, taken with food. The purpose was polyp reduction; the mechanism is blocking COX-2 and lowering prostaglandin-driven cell proliferation. Side effects include cardiovascular events, hypertension, oedema, and GI bleeding, especially with long-term use. [1] [2]
2. Sulindac
Sulindac is a non-selective NSAID that has been shown in trials and case series to cause partial regression of colorectal and rectal polyps in FAP. Doses used in studies were often 150–200 mg twice daily in adults. The purpose is chemoprevention, not a cure or replacement for colectomy. Mechanistically, sulindac reduces prostaglandin synthesis and may trigger apoptosis in adenoma cells. Common side effects are gastric irritation, ulcer, kidney dysfunction, and, rarely, liver injury. [2] [3]
3. Erlotinib
Erlotinib is an EGFR tyrosine kinase inhibitor studied in FAP for duodenal and colorectal polyp reduction, often combined with sulindac. Regimens include daily or weekly dosing (for example, 75–150 mg on certain schedules), tailored by trial protocols. The purpose is to slow polyp growth in high-risk upper-GI disease. The mechanism is EGFR pathway inhibition, which reduces cell proliferation. Side effects include acne-like rash, diarrhoea, fatigue, and, rarely, lung or liver toxicity. [3] [4]
4. Combination sulindac + erlotinib
This combination has shown marked reductions in duodenal and colorectal polyp burden in phase 2 trials. Typical regimens use standard sulindac dosing plus erlotinib at doses adjusted for tolerability. The purpose is stronger chemopreventive effect than either drug alone. The mechanism is dual blockade of COX-2–related inflammation and EGFR signalling. Side effects often include skin rash, diarrhoea, mouth sores, and, occasionally, more serious toxicities that limit long-term use. [4] [5]
5. Aspirin (low-dose)
Low-dose aspirin (for example 75–100 mg once daily) is widely used for cardiovascular prevention and has evidence for reducing sporadic colorectal cancer risk. In FAP, its use may be considered on a case-by-case basis as an additional chemopreventive measure. The mechanism is COX inhibition and reduction of pro-inflammatory prostaglandins. Main side effects are stomach irritation and increased bleeding risk, especially when combined with other NSAIDs or anticoagulants. [6]
6. 5-Fluorouracil (5-FU)
5-FU is a standard chemotherapy drug for colorectal cancer, including cancers that arise in FAP. It is usually given intravenously in cycles (for example, 425–500 mg/m²/day for several days, depending on protocol) together with other agents. The purpose is to kill rapidly dividing cancer cells. Mechanistically, 5-FU is a pyrimidine analogue that interferes with DNA synthesis. Side effects include mouth sores, diarrhoea, low blood counts, hair thinning, and hand-foot syndrome. [7]
7. Capecitabine
Capecitabine is an oral prodrug converted to 5-FU inside tumor tissues. Typical regimens use doses such as 1,000–1,250 mg/m² twice daily for 14 days in 21-day cycles, adjusted individually. The purpose is to offer 5-FU-like activity via tablets instead of continuous infusions. The mechanism is tumour-targeted activation by thymidine phosphorylase. Common side effects are diarrhoea, hand-foot syndrome, fatigue, and bone-marrow suppression. [8]
8. Oxaliplatin
Oxaliplatin is a platinum-based chemotherapy used in combinations like FOLFOX for colorectal cancer. Doses such as 85 mg/m² every two weeks with 5-FU and leucovorin are common. The purpose is to improve survival when colorectal cancer has developed. Mechanistically, it forms DNA cross-links that block replication in cancer cells. Side effects include peripheral neuropathy (numbness, tingling), nausea, low blood counts, and allergic reactions. [9]
9. Irinotecan
Irinotecan is a topoisomerase I inhibitor used in regimens such as FOLFIRI. Common dosing is around 180 mg/m² every two weeks with 5-FU and leucovorin, adjusted for tolerance. The purpose is to treat advanced colorectal cancer. The mechanism is inhibition of topoisomerase I, leading to DNA breaks in dividing cells. Main side effects are diarrhoea (early and late), neutropenia, hair loss, and fatigue. [10]
10. Leucovorin (folinic acid)
Leucovorin is not a traditional chemotherapy but enhances the binding of 5-FU to its target enzyme. It is given intravenously or orally alongside 5-FU at various doses in standard regimens. The purpose is to boost the effectiveness of 5-FU in colorectal cancer therapy. Mechanistically, leucovorin stabilises the 5-FU–thymidylate synthase complex. Side effects largely mirror those of 5-FU, including GI upset and myelosuppression. [11]
11. Bevacizumab
Bevacizumab is a monoclonal antibody against VEGF used with chemotherapy for advanced colorectal cancer. It is given as an intravenous infusion (for example 5–10 mg/kg every 2–3 weeks). The purpose is to starve tumours of blood supply. Mechanistically, it blocks VEGF-mediated angiogenesis. Side effects include high blood pressure, bleeding, delayed wound healing, protein in urine, and, rarely, bowel perforation. [12]
12. Cetuximab
Cetuximab is an anti-EGFR monoclonal antibody used in RAS wild-type metastatic colorectal cancer. It is infused intravenously on weekly or bi-weekly schedules, with a loading dose followed by maintenance doses. The purpose is to inhibit EGFR-driven tumour growth. The mechanism is receptor blockade on tumour cells. Side effects include acne-like rash, infusion reactions, low magnesium, and diarrhoea. [13]
13. Panitumumab
Panitumumab is another anti-EGFR antibody used in KRAS/NRAS wild-type metastatic colorectal cancer. It is given intravenously every two weeks at weight-based doses. The purpose and mechanism are similar to cetuximab: blocking EGFR to slow tumour growth. Side effects include rash, nail changes, dry skin, eye irritation, and electrolyte disturbances. [14]
14. Nivolumab
Nivolumab is a PD-1 immune checkpoint inhibitor used in some microsatellite-instability-high or mismatch-repair-deficient colorectal cancers, which can occur in polyposis syndromes. It is given as an IV infusion at fixed doses every few weeks. The purpose is to “release the brakes” on T-cells so they can attack cancer. The mechanism is PD-1 blockade on T-cells. Side effects include immune-related inflammation of lungs, gut, liver, or endocrine glands. [15]
15. Pembrolizumab
Pembrolizumab is another PD-1 inhibitor used for MSI-H/dMMR colorectal cancer. It is infused every three or six weeks at fixed doses. The purpose is long-lasting immune control of advanced disease. The mechanism is similar to nivolumab: PD-1 blockade and activation of anti-tumour immunity. Side effects can include colitis, hepatitis, thyroid problems, skin rash, and fatigue. [16]
16. Regorafenib
Regorafenib is an oral multi-kinase inhibitor used later-line in metastatic colorectal cancer. A typical regimen is 80–160 mg once daily for 21 days of a 28-day cycle, with cautious dose escalation. The purpose is disease control when standard chemotherapy has failed. Mechanistically, it blocks several kinases involved in angiogenesis and tumour growth. Side effects include hand-foot reaction, hypertension, fatigue, diarrhoea, and liver toxicity. [17]
17. Trifluridine/tipiracil (TAS-102)
TAS-102 combines a nucleoside analogue (trifluridine) with tipiracil to increase its bioavailability, used in refractory metastatic colorectal cancer. Doses are based on body surface area and given orally on specific days of a 28-day cycle. The purpose is to prolong survival when other treatments have stopped working. Mechanism: incorporation into DNA and interference with replication. Side effects: neutropenia, anaemia, fatigue, and gastrointestinal upset. [18]
18. Ferrous sulfate (oral iron)
Chronic bleeding from numerous polyps can cause iron-deficiency anaemia. Oral iron (for example 100–200 mg elemental iron per day, in divided doses) can be prescribed. The purpose is to replenish iron stores and improve fatigue and breathlessness. Mechanistically, iron is absorbed in the gut and used for haemoglobin production. Side effects include constipation, dark stools, and stomach discomfort. [19]
19. Parenteral iron preparations
If oral iron is not tolerated or effective, intravenous iron (such as ferric carboxymaltose or iron sucrose) may be used under hospital supervision. Doses are calculated based on weight and haemoglobin deficit. The purpose is faster correction of severe anaemia. The mechanism bypasses the gut and directly raises iron stores. Side effects include infusion reactions, transient flu-like symptoms, and, rarely, severe allergy. [20]
20. Proton pump inhibitors (PPIs) for upper-GI protection
PPIs like omeprazole are often used in FAP patients on NSAIDs or with duodenal disease to reduce acid and protect the lining. Common doses are 20–40 mg once daily. The purpose is to lower ulcer and bleeding risk. Mechanistically, PPIs block the proton pump in stomach parietal cells, reducing acid secretion. Side effects include headache, diarrhoea, and, with long-term use, possible mineral and vitamin B12 deficiencies. [21]
Dietary Molecular Supplements
1. Calcium
Calcium supplements (for example 500–1,000 mg/day total from diet plus pills) have been studied for modest colorectal polyp risk reduction. The purpose is to support bone health and possibly bind harmful bile acids in the colon. Mechanistically, calcium can form insoluble soaps with fatty acids and bile acids, reducing direct irritation of colon cells. Excess intake can cause kidney stones or constipation, so dosing should follow medical advice. [1]
2. Vitamin D
Vitamin D (often 800–2,000 IU/day, adjusted to blood levels) supports bone health and may have anti-proliferative effects on colon cells. The purpose is to maintain sufficient blood vitamin D and possibly support a healthier mucosal environment. Mechanistically, vitamin D receptors in colon cells influence cell growth, differentiation, and immune responses. High doses without monitoring can cause high calcium and kidney problems, so testing is important. [2]
3. Omega-3 fatty acids (fish oil/EPA)
Omega-3 supplements (for example 1–2 g/day of EPA/DHA) have anti-inflammatory effects. The purpose is to reduce chronic inflammation and support heart and gut health. Mechanistically, omega-3s compete with omega-6 fatty acids in cell membranes, producing less inflammatory eicosanoids. Potential side effects include mild stomach upset and a slightly increased bleeding tendency at high doses, especially with anticoagulants. [3]
4. Curcumin (from turmeric)
Curcumin (often 500–1,500 mg/day in divided doses in trials) has antioxidant and anti-inflammatory properties. The purpose is experimental chemoprevention support, not a replacement for surgery. Mechanistically, curcumin can modulate multiple signalling pathways involved in cell growth and apoptosis. Absorption is low, so many products combine it with piperine or use special formulations. Side effects are usually mild, such as nausea or diarrhoea at high doses. [4]
5. Green tea extract (EGCG)
Green tea catechins like EGCG (for example 200–400 mg/day in some studies) may have anti-oxidant and anti-proliferative effects. The purpose is to support general cell health. Mechanistically, EGCG can reduce oxidative stress and affect cell-cycle regulators in colon cells in laboratory studies. High doses have been linked to rare liver toxicity, so products should be from reputable sources and used cautiously. [5]
6. Probiotics
Probiotics containing Lactobacillus and Bifidobacterium strains are used at doses such as 10⁹–10¹⁰ CFU/day. The purpose is to support a balanced gut microbiome, especially after surgery or antibiotics. Mechanistically, probiotics may compete with harmful bacteria, produce beneficial metabolites, and improve barrier function. Most people tolerate them well, but severely immunocompromised patients should discuss risks with their doctor. [6]
7. Soluble fibre (psyllium or inulin)
Psyllium (for example 5–10 g/day) or inulin can be used to increase soluble fibre intake. The purpose is to normalise stool consistency and support gut bacteria that produce short-chain fatty acids. Mechanistically, these fibres ferment in the colon, feeding beneficial microbes. Side effects are usually gas and bloating when started quickly, so doses are increased slowly with plenty of water. [7]
8. Multivitamin with B-complex
A standard multivitamin with B-vitamins helps cover nutritional gaps, especially after bowel surgery when absorption might change. The purpose is to prevent deficiencies of folate, B12, and others. Mechanistically, B-vitamins support DNA repair and normal cell division. Very high separate doses of folic acid are controversial in colorectal neoplasia, so routine moderate multivitamin doses are safer unless a doctor prescribes more. [8]
9. Selenium (low dose)
Selenium, often 50–100 µg/day in a multivitamin, has been studied for cancer prevention. The purpose is to support antioxidant enzyme systems. Mechanistically, selenium is part of glutathione peroxidase and other enzymes that reduce oxidative damage. Higher doses can cause hair loss, nail changes, and garlic-like breath, so any extra selenium should be carefully discussed with a clinician. [9]
10. Vitamin C and E (within recommended limits)
Vitamin C (for example 200–500 mg/day) and vitamin E (around 15–30 IU/day) act as antioxidants. The purpose is to support general health and reduce oxidative stress. Mechanistically, they neutralise free radicals that can damage DNA and cell membranes. Very high doses of vitamin E have been linked to harm in some trials, so balanced, moderate supplementation is preferred over “mega-doses.” [10]
Immunity-Boosting and Regenerative / Stem-Cell-Related Drugs
Important: There are currently no approved “stem cell drugs” specifically for FAP itself. The agents below support the immune system or blood cell recovery in people who receive chemotherapy for cancers that may occur in FAP. They are hospital-only medicines.
1. Filgrastim (G-CSF)
Filgrastim is an injected growth factor used at doses such as 5 µg/kg/day after chemotherapy. The purpose is to boost neutrophil counts and lower infection risk when bone marrow is suppressed. Mechanistically, it stimulates the bone marrow to produce and release neutrophils. Side effects include bone pain, injection-site reactions, and, rarely, spleen enlargement or rupture. [1]
2. Pegfilgrastim
Pegfilgrastim is a long-acting form of G-CSF, usually given as a single injection once per chemo cycle. The purpose is similar to filgrastim but with more convenient dosing. Mechanistically, pegylation slows kidney clearance, providing sustained stimulation of neutrophil production. Side effects are similar, including bone pain and, rarely, serious allergic or splenic events. [2]
3. Epoetin alfa or darbepoetin
These erythropoiesis-stimulating agents (ESAs) are injected to treat certain cases of chemotherapy-induced anaemia. Doses depend on weight and haemoglobin levels and are adjusted over weeks. The purpose is to reduce transfusion needs. Mechanistically, ESAs mimic erythropoietin and stimulate red blood cell production in bone marrow. Side effects include high blood pressure, increased clot risk, and, in some patients, worse cancer outcomes if overused, so they are used cautiously. [3]
4. Immune checkpoint inhibitors as immune “re-activators”
Drugs like nivolumab and pembrolizumab (already described above) also belong to immune-boosting therapies. The purpose is to re-activate the body’s anti-tumour immunity in MSI-H/dMMR colorectal cancers. Mechanistically, they block PD-1, removing inhibitory signals on T-cells. Side effects are immune-related inflammations of organs such as lungs, gut, liver, or thyroid, sometimes serious and requiring steroids. [4]
5. Autologous stem cell support in selected cancers
In very rare situations, high-dose chemotherapy for certain cancers uses autologous stem cell collection and reinfusion to rescue the bone marrow. The purpose is to allow more intensive cancer therapy. Mechanistically, patient stem cells are collected, frozen, and later infused back to repopulate the marrow. This approach is not routine for FAP-related colorectal cancer and is mentioned only as a general concept in oncologic care. [5]
6. Nutritional and infection-prevention protocols during chemotherapy
Though not a classic “drug,” coordinated use of vaccines (like flu and pneumonia shots when appropriate), antimicrobial prophylaxis in high-risk periods, and optimised nutrition helps keep immunity stronger during treatment. The purpose is to lower infection risk and support tissue healing. Mechanistically, vaccines prime the immune system, and targeted antibiotics or antivirals protect during neutropenia. These must be timed carefully by oncology teams. [6]
Surgeries (Main Procedures and Why They Are Done)
1. Total proctocolectomy with ileal pouch–anal anastomosis (IPAA)
This operation removes the entire colon and rectum, then uses the end of the small intestine to create a pouch joined to the anus. The purpose is to remove virtually all colorectal mucosa at risk of cancer while preserving anal continence. Mechanistically, the pouch acts as a new reservoir for stool. It is often chosen for young, fit patients with extensive rectal polyps. [1]
2. Colectomy with ileorectal anastomosis (IRA)
In this surgery, the colon is removed but the rectum is left and joined directly to the small bowel. The purpose is to reduce cancer risk while keeping rectal function and sometimes better bowel control. Mechanistically, the remaining rectum must be closely surveilled with frequent endoscopy because polyps and cancers can still develop there. It is considered when rectal polyp burden is relatively low and controllable. [2]
3. Subtotal colectomy or segmental resections in selected cases
Sometimes, especially when the disease pattern or other health problems are unusual, surgeons may remove most of the colon but leave a portion for functional reasons. The purpose is to balance cancer risk, symptoms, and quality of life. Mechanistically, this leaves some mucosa at risk, so lifelong surveillance remains critical. It is less common in classic FAP than in attenuated forms. [3]
4. Duodenectomy or pancreas-sparing duodenal surgery
For advanced duodenal or ampullary polyps with high-grade dysplasia or early cancer, removal of the affected duodenum (sometimes with preservation of the pancreas) may be needed. The purpose is to prevent or treat upper-GI cancer. Mechanistically, surgeons remove the segment containing high-risk polyps and reconnect the digestive tract. These are complex operations done in specialised centres. [4]
5. Surgery for desmoid tumours or thyroid cancer
FAP can cause desmoid tumours in the abdomen and increase thyroid cancer risk. When these cause pain, obstruction, or proven malignancy, surgical removal may be offered. The purpose is to relieve symptoms and remove cancer. Mechanistically, surgeons carefully excise the tumour, sometimes with margins of normal tissue. Desmoids can recur, so surgery is balanced against the risk of stimulating more growth. [5]
Prevention and Risk Reduction
Know your family history and ask for genetic evaluation early. Early APC testing in at-risk relatives allows colonoscopy and prevention to start in time, before symptoms. [1]
Follow the recommended surveillance schedule strictly. Never skip colonoscopies or upper-GI endoscopies; they are the core of cancer prevention in FAP. [2]
Plan prophylactic colectomy at the right time. Work with your team to choose surgery before cancer appears but after careful preparation for life after surgery. [3]
Avoid smoking and limit alcohol. These lifestyle factors add extra cancer and heart risk that FAP patients do not need on top of their genetic risk. [4]
Maintain a healthy weight and stay active. Regular movement and weight control support bowel function, heart health, and recovery from surgery or chemotherapy. [5]
Choose a balanced, plant-rich diet. Emphasise vegetables, fruits, whole grains, and legumes while limiting processed meat and very fatty, fried foods. [6]
Use NSAIDs only under specialist advice. Drugs like celecoxib or sulindac should never be self-started for FAP; they have serious risks and do not replace surgery. [7]
Keep vaccination and infection prevention up to date. This is especially important before and after major surgery or during chemotherapy to reduce complications. [8]
Engage with a hereditary cancer clinic if possible. Specialist centres provide up-to-date guidelines, trials, and psychosocial support that can improve long-term outcomes. [9]
Share information with family members. Let close relatives know about the diagnosis so they can seek counselling and testing, reducing undiagnosed risk in the family. [10]
When to See Doctors
You should see a doctor urgently if you notice rectal bleeding, black or very dark stools, sudden changes in bowel habits (such as persistent diarrhoea or constipation), severe or cramping abdominal pain, vomiting, or unexplained weight loss. [1] People with known FAP or an APC mutation should keep regular appointments even when they feel well, because dangerous polyps often cause no symptoms. You should also contact your team if you develop new jaundice, difficulty swallowing, or a neck lump, which can signal upper-GI or thyroid problems needing assessment. [2]
What to Eat and What to Avoid
Eat: plenty of colourful vegetables and fruits every day. Avoid: relying on processed snacks and sugary drinks as daily staples. [1]
Eat: whole grains like brown rice, oats, and whole-wheat bread. Avoid: large amounts of refined white bread, pastries, and sweets. [2]
Eat: plant proteins such as beans, lentils, tofu, and nuts. Avoid: eating processed meats (sausages, hot dogs, bacon) regularly. [3]
Eat: modest portions of fish and skinless poultry. Avoid: very frequent large portions of red meat, especially charred or grilled at high heat. [4]
Eat: foods rich in calcium (low-fat dairy, fortified plant milks, leafy greens) if tolerated. Avoid: excessive calcium tablets without medical advice. [5]
Eat: small, regular meals after surgery to keep stool output steady. Avoid: huge, heavy meals that overload your pouch or stoma. [6]
Eat: enough fluids, especially water and oral rehydration solutions when output is high. Avoid: drinking mostly alcohol or very sugary drinks, which can worsen dehydration. [7]
Eat: soluble fibre (oats, bananas, cooked carrots) to help thicken stool if you have loose output. Avoid: too much insoluble fibre (raw cabbage, popcorn) right after surgery until your team says it is safe. [8]
Eat: probiotic-rich foods like yoghurt with live cultures if tolerated. Avoid: unpasteurised or high-risk foods if your immune system is weak from chemotherapy. [9]
Eat: in a way that keeps your weight stable and energy good. Avoid: extreme “cancer cure” diets that cut out whole food groups or promise to replace surgery or medical treatment. [10]
Frequently Asked Questions
1. Can diet or medicines alone cure classic FAP?
No. Diet and medicines can support health and sometimes reduce polyp number, but they cannot fully remove the very high cancer risk from the APC mutation. Prophylactic colectomy and lifelong surveillance remain the cornerstone of care. [1]
2. At what age do colon polyps usually appear in FAP?
In classic FAP, polyps often start appearing in the teenage years, sometimes even earlier. That is why guidelines recommend starting lower-GI surveillance around age 10–12 in at-risk children, so polyps can be caught before cancer develops. [2]
3. If my APC test is negative, am I completely safe?
If a clearly disease-causing APC mutation has been found in the family and your test is negative, your colorectal cancer risk usually drops back to that of the general population. However, your doctor may still recommend standard population screening, such as colonoscopy at the usual ages. [3]
4. Do all people with FAP need surgery?
For classic FAP, virtually everyone will eventually need colectomy, because the lifetime colorectal cancer risk is almost 100% if the colon is left in place. The exact timing and type of surgery are individual and based on polyp burden, age, and preferences. [4]
5. Will I need a permanent stoma?
Not always. Many patients can have an ileal pouch–anal anastomosis that allows them to pass stool through the anus. Some will need a temporary or permanent stoma depending on anatomy, disease, and surgical decisions. Your surgeon will explain the options and expected function. [5]
6. How often will I need endoscopy after colectomy?
Even after colectomy, regular surveillance continues. The remaining rectum or pouch and the duodenum are checked at intervals based on guideline risk scores and previous findings, often every 1–3 years. [6]
7. Are celecoxib or sulindac safe long term?
These NSAIDs can reduce polyp burden but have important risks, including cardiovascular events, kidney problems, and GI bleeding. In fact, the FAP indication for celecoxib has been withdrawn in some regions. They are used only under expert supervision and never as stand-alone treatment. [7]
8. Can I play sports after surgery?
Most people gradually return to normal physical activity after recovery, and exercise is encouraged. You may need to avoid heavy lifting for some months and protect any stoma. Your surgical team will give personalised advice based on healing and overall health. [8]
9. Will FAP affect my ability to have children?
Fertility is often preserved, especially with careful surgical planning, but pelvic surgery can sometimes affect fertility. There is also the 50% chance of passing on the APC mutation. Pre-conception counselling can discuss fertility preservation and options like PGD. [9]
10. Are there new treatments or trials for FAP?
Yes. Trials are exploring combinations such as sulindac plus erlotinib and other targeted or immune-based strategies to reduce polyp burden. These are usually available in specialist centres and do not replace surgery but may delay or complement it. [10]
11. Do I still need screening for other cancers?
Yes. People with FAP need tailored surveillance for duodenal disease, thyroid cancer, and sometimes other extra-colonic manifestations such as desmoid tumours. Your team will build a schedule for these sites as well as the colon or pouch. [11]
12. Can children be tested for APC mutations?
In families with known mutations, testing is usually offered in later childhood, around the age where colonoscopy would begin. This allows time for counselling and planning but avoids unnecessary anxiety in very young children who would not yet change management. [12]
13. Is attenuated FAP the same as classic FAP?
No. Attenuated FAP tends to have fewer polyps, later onset, and slightly different risk patterns. However, it still carries a high cancer risk and needs dedicated surveillance and planning, guided by genetic and clinical features. [13]
14. Can I ever stop seeing specialists?
No. FAP is lifelong, and even after colectomy, there is ongoing risk in the rectum or pouch, duodenum, and extra-colonic organs. Lifelong follow-up with a hereditary cancer team is essential to stay ahead of new problems. [14]
15. What is the most important thing I can do right now?
The single most important step is to connect with an experienced specialist or hereditary cancer clinic, follow their surveillance and surgery plan exactly, and involve your family in counselling and testing when appropriate. Medicines, supplements, and lifestyle changes are useful additions but cannot replace expert care. [15]
Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.
The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: January 27, 2025.
