Fast Five Quiz: Colorectal Cancer Screening

Ali Alqahtani, MD; Leyla Ghazi, MD


January 27, 2023

Approximately 3%-5% of all cases of CRC are associated with an identifiable inherited CRC syndrome such as FAP. Nearly all patients with untreated classic FAP will develop CRC by the age of 40 years.

Generally, a diagnosis of FAP can be established when > 100 synchronous adenomas are found. Clinical Practice Guidelines published in 2017 by the ASCRS, as well as guidelines published in 2015 by the ACG, recommend germline testing of the APC gene for individuals with > 20 lifetime adenomas, in part to facilitate screening for this mutation in family members. Inactivating mutations of this tumor suppressor gene initiate most cases of CRC.

When a family member has been diagnosed with FAP with a known mutation, the patient's at-risk family members can be screened for this mutation only, as opposed to undergoing the slower and more expensive process of multigene panel sequencing. According to the ACG, individuals at risk for or affected with the classic adenomatous polyposis syndromes should be screened annually for CRC using colonoscopy or flexible sigmoidoscopy beginning at puberty. The ASCRS calls for flexible sigmoidoscopy every 1-2 years for children at risk for classic FAP, beginning at 10-12 years of age.

Both societies' guidelines recommend using colonoscopy to screen for CRC in patients with attenuated FAP, a milder form of the syndrome in which patients have the APC mutation but have fewer (< 100) synchronous adenomas than in classic FAP.

Learn more about CRC and FAP screening.

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