What are the recommended screening programs for Familial Adenomatous Polyposis (FAP)?

Recommended Screening Programs for Familial Adenomatous Polyposis (FAP)

For individuals with FAP, screening should begin in early adolescence with flexible sigmoidoscopy every 1-2 years starting at age 10-14 years and continue lifelong in mutation carriers to reduce colorectal cancer morbidity and mortality. 1

Genetic Testing and Initial Screening

• Genetic counseling and APC mutation analysis should be offered to all patients with suspected FAP, as identifying the causative mutation allows for targeted screening of at-risk family members 1
• Full germline genetic testing of APC should include DNA sequencing and large rearrangement analysis 1
• In families where the causative mutation is identified, presymptomatic testing should be offered to first-degree relatives 1
• When no mutation is identified, all at-risk family members should undergo colorectal screening 1

Colorectal Screening Protocols

For Classical FAP:

• Flexible sigmoidoscopy or colonoscopy every 1-2 years starting at age 10-11 years and continued lifelong in mutation carriers 1, 2
• Once adenomas are detected, annual colonoscopy should be performed until colectomy is planned 1
• Surgery is indicated when there are large numbers of adenomas or adenomas showing high-grade dysplasia 1
• In at-risk individuals from families without an identified APC mutation, surveillance should be carried out every 2 years until age 40, every 3-5 years between 40-50 years, and may be discontinued at age 50 if no polyposis develops 1

For Attenuated FAP (AFAP):

• Total colonoscopy (not just sigmoidoscopy) every 2 years starting at age 18-20 years and continued lifelong in mutation carriers 1
• Once adenomas are detected, annual colonoscopy should be performed 1
• Some patients with AFAP can be conservatively managed with colonoscopy every 1-2 years and polypectomy 1

Screening for Extracolonic Manifestations

• Gastroduodenal endoscopy using both front and side-view scopes should be performed when colorectal polyposis is diagnosed or at age 25-30 years, whichever comes first 1, 2
• Surveillance intervals for upper GI screening are based on the Spigelman stage (severity of duodenal polyposis) 1
• Annual cervical ultrasonography is recommended for thyroid cancer screening 2
• Regular physical examination and abdominal CT should be performed for desmoid tumors, especially in patients with a family history of desmoids or after abdominal surgery 2

Post-Surgical Surveillance

• After colorectal surgery, surveillance of the rectum or pouch should be carried out every 6-12 months if rectal tissue remains 1
• For patients with ileoanal pouch, surveillance should be performed every 6 months to 5 years depending on polyp burden 1
• The decision on the type of colorectal surgery (total colectomy with ileorectal anastomosis vs. proctocolectomy with ileal pouch-anal anastomosis) depends on the patient's age, severity of rectal polyposis, desire for children, risk of developing desmoids, and possibly the site of the mutation in the APC gene 1, 2

Special Considerations

• Patients with mutations between codons 1250 and 1464, especially codon 1309, have a more severe form of FAP and may require more aggressive surveillance 1, 3
• Patients with mutations within codons 1055 and 1262 may have a higher risk of developing advanced colorectal carcinomas and require special attention 3
• In approximately 30-40% of FAP cases, there is no family history, suggesting a de novo mutation origin 1
• Attention must be paid to FAP-related symptoms (increasing bowel frequency, rectal bleeding, mucous discharge) in children at risk, especially those with mutations at codon 1309 who may develop severe polyposis before age 10 1

Implementing these screening protocols has been shown to reduce colorectal cancer incidence and mortality in FAP patients by allowing early detection and intervention before malignant transformation occurs 1.