American Board of Internal Medicine (ABIM) Certification Practice Exam

What screening is recommended for all newly diagnosed patients with colorectal cancers?

1. Genetic testing for BRCA mutations

2. MMR deficiency testing for Lynch syndrome

3. Endoscopic ultrasonography

4. CT scans every year

The correct answer is: MMR deficiency testing for Lynch syndrome

Screening for microsatellite instability (MSI) or mismatch repair (MMR) deficiency is recommended for all newly diagnosed patients with colorectal cancers as it helps identify those with Lynch syndrome, a hereditary condition that significantly increases the risk of developing colorectal and other types of cancer. Identifying MMR deficiency is crucial because it can guide clinical management strategies, including the potential for more targeted surveillance for other associated malignancies, considerations for immunotherapy options, and informing family members about genetic counseling and testing. The option of genetic testing for BRCA mutations primarily applies to breast and ovarian cancers, rather than colorectal cancer. Endoscopic ultrasonography is typically reserved for examining local extension or staging of rectal tumors rather than routine screening in newly diagnosed colorectal cancer patients. While annual CT scans may be part of the follow-up for surveillance of recurrence in colorectal cancers, they are not a screening recommendation at the time of initial diagnosis. Therefore, the focus on MMR deficiency testing is essential for appropriate management and risk assessment in newly diagnosed colorectal cancer patients.