When should you screen someone for Familial Adenomatous Polyposis (FAP)?

From the Guidelines

Screening for Familial Adenomatous Polyposis (FAP) should be considered for individuals with a family history of FAP, starting at the age of 10 to 11 years for classic FAP and 18 to 20 years for attenuated FAP, with lifelong surveillance in mutation carriers. This approach is based on the most recent and highest quality study, which recommends sigmoidoscopy or colonoscopy every 1 to 2 years for individuals with classic FAP, and colonoscopy every 2 years for those with attenuated FAP 1.

Key considerations for screening include:

• Family history of FAP
• Presence of more than 100 colorectal adenomatous polyps
• Known APC gene mutations
• Starting age for screening: 10-11 years for classic FAP and 18-20 years for attenuated FAP
• Surveillance frequency: every 1-2 years for classic FAP and every 2 years for attenuated FAP

Additionally, screening should also consider extracolonic manifestations, such as gastroduodenal polyposis, thyroid cancer, and desmoid tumors, starting at the age of 25 to 30 years or when colorectal polyposis is diagnosed, whichever comes first 1. Early screening is crucial because FAP leads to a high lifetime risk of colorectal cancer if left untreated.

The condition follows an autosomal dominant inheritance pattern, so children of affected individuals have a 50% chance of inheriting the mutation, making family screening essential. While an older study suggests starting screening at age 12-15 years 1, the more recent and higher quality study recommends starting at age 10-11 years for classic FAP and 18-20 years for attenuated FAP 1.

From the Research

Screening for FAP

• Screening for Familial Adenomatous Polyposis (FAP) is crucial for early detection and management of the disease 2, 3, 4, 5, 6
• The ideal time to screen for FAP is not explicitly stated, but it is recommended that individuals with a family history of FAP undergo screening at a young age, typically before the age of 20 2
• A study suggests that most children with FAP are asymptomatic and are diagnosed via screening due to family history, with a mean age of diagnosis of 12.5 years 2
• Another study recommends that individuals with FAP undergo prophylactic colectomy, typically by the age of 40, to reduce the risk of colorectal cancer 3
• Screening adherence, genetic testing, and other health behaviors among individuals with FAP and their relatives are not well characterized, highlighting the need for further research 4

Genetic Testing

• Genetic testing is an important tool for diagnosing FAP, with 53% of individuals with FAP undergoing genetic testing, which confirmed APC mutation in 88% of cases 2
• The APC gene contains 15 coding exons, and the mutation spectrum of the APC gene is broad, with 87% of causative mutations being point mutations and around 10% to 15% being intragenic deletions and duplications 5
• Next generation sequencing (NGS)-based targeted gene analysis has become clinically available for detection of point mutations and other sequence variants in the APC gene 5

Impact of Screening

• Screening of family members of FAP patients has been shown to significantly influence survival, with a study finding that survival of screened family members is comparable to the general population within 20 years after diagnosis 6
• The study also found that over two thirds of all deaths were FAP related, highlighting the importance of early detection and management of the disease 6