What is the routine screening protocol for individuals with Familial Adenomatous Polyposis (FAP)?

Routine Screening Protocol for Familial Adenomatous Polyposis (FAP)

For individuals with FAP, screening should begin with sigmoidoscopy every 1-2 years starting at age 10-12 years and continue lifelong in mutation carriers, with annual colonoscopy once adenomas are detected until colectomy is planned. 1

Initial Genetic Testing and Risk Assessment

• Patients with multiple colorectal adenomas (>10) should undergo germline genetic testing of APC and/or MUTYH genes 1
• Full germline genetic testing should include DNA sequencing and large rearrangement analysis 1
• For MUTYH testing in Caucasian populations, screening can begin with the most common mutations (G396D, Y179C) followed by analysis of the entire gene in heterozygotes 1
• Gene testing should commence with an affected individual; if the causative mutation is detected, presymptomatic diagnosis can be offered to at-risk family members 1

Screening Protocol Based on FAP Type

Classic FAP

• Colorectal screening:

  • Sigmoidoscopy or colonoscopy every 1-2 years starting at age 10-12 years 1
  • Once adenomas are detected, annual colonoscopy until colectomy is planned 1
  • Surgery is indicated when there are large numbers of adenomas or adenomas showing high-grade dysplasia 1

• Upper GI screening:

  • Gastroduodenal endoscopy using both front and side-view scopes starting when colorectal polyposis is diagnosed or at age 25-30 years, whichever comes first 1
  • Surveillance intervals based on Spigelman stage (polyp burden) 1

Attenuated FAP (AFAP)

• Colorectal screening:

  • Total colonoscopy (not just sigmoidoscopy) every 2 years starting at age 18-20 years 1
  • Some patients can be managed conservatively with annual colonoscopy and polypectomy 1

• Upper GI screening: Same as classic FAP

MUTYH-Associated Polyposis (MAP)

• Surveillance protocol similar to that for patients with AFAP 1
• Colonoscopy every 2 years, starting at age 18-20 years and continuing lifelong in mutation carriers 1

Extracolonic Manifestation Screening

In both classic and attenuated FAP, screening for extracolonic manifestations should begin when colorectal polyposis is diagnosed or at age 25-30 years, whichever comes first 1:

• Gastroduodenal polyposis: Endoscopy every 6 months to 5 years depending on polyp burden 1
• Thyroid cancer: Annual cervical ultrasonography 1
• Desmoid tumors: Regular physical examination and abdominal CT, especially in patients with positive family history or after abdominal surgery 1

Post-Surgical Surveillance

• After colorectal surgery, surveillance of the rectum or pouch should be performed 1
• For retained rectum after (sub)total colectomy: every 6-12 months 1
• For ileal pouch after proctocolectomy: every 6 months to 5 years depending on polyp burden 1

Important Clinical Considerations

• The decision on the type of colorectal surgery (total colectomy with ileorectal anastomosis vs. proctocolectomy with ileal pouch-anal anastomosis) depends on:

  • Patient age
  • Severity of rectal polyposis
  • Desire to have children
  • Risk of developing desmoids
  • Site of mutation in the APC gene 1

• Patients with a specific mutation at codon 1309 in exon 15 of the APC gene may have a more severe phenotype with earlier onset of polyps and increased cancer risk 2

Pitfalls to Avoid

1. Delaying screening: Cancer can develop in childhood in severe phenotypes, particularly with certain mutations 2
2. Using sigmoidoscopy alone for AFAP: AFAP requires full colonoscopy due to the proximal distribution of polyps 1
3. Neglecting extracolonic manifestations: These can become the main cause of mortality in patients who have undergone prophylactic colectomy 2
4. Inadequate post-surgical surveillance: Continued monitoring of remaining rectal tissue or pouch is essential 1
5. One-size-fits-all approach: The screening protocol should consider the specific mutation, family history of early-onset disease, and phenotypic expression 1, 2

By following these evidence-based guidelines, the risk of colorectal cancer in FAP patients can be significantly reduced, allowing focus on the management of other manifestations of the syndrome that impact long-term survival and quality of life.