The most appropriate screening strategy for this patient is yearly fecal immunochemical testing (FIT). Annual stool testing for occult blood using either high-sensitivity guaiac fecal occult blood testing (gFOBT) or FIT is an acceptable colon cancer screening strategy in average-risk patients. Randomized controlled trials have shown statistically significant reductions in colorectal cancer incidence (17%-20%) and mortality (15%-33%) with regular gFOBT screening. Limitations of gFOBT screening include low sensitivity for advanced adenomas (11%-41%), diet and medication interactions that may produce false-positive or false-negative results, and the need for appropriate diagnostic follow-up (that is, colonoscopy) if test results are positive to achieve maximum benefit. FIT uses specific antibodies to detect globin in the stool and is generally considered to be a more sensitive study than guaiac-based testing. In cross-sectional studies, FIT sensitivity has ranged from 60% to 85% for colorectal cancer and 25% to 50% for advanced adenomas. Pretest dietary restrictions are not necessary. As with gFOBT, FIT requires appropriate diagnostic follow-up for positive results.

In a 2016 statement, the U.S. Preventive Services Task Force (USPSTF) reaffirmed its recommendation to screen all adults aged 50 to 75 years for colorectal cancer (Bibbins-Domingo K et al, 2016). The USPSTF found no head-to-head studies demonstrating that a particular screening strategy was more effective than another; however, the screening strategies have varying levels of evidence supporting their efficacy, as well as different benefits and risks. In contrast to the 2008 USPSTF recommendation statement on colorectal cancer screening, which emphasized specific screening tests and intervals, the 2016 USPSTF recommendation statement stresses that patients should be offered a choice in screening strategies to potentially increase the total number of persons screened. Acceptable screening strategies include high-sensitivity fecal occult blood testing (gFOBT or FIT) every year, flexible sigmoidoscopy every 5 years, CT colonography every 5 years, combined flexible sigmoidoscopy every 10 years with high-sensitivity fecal occult blood testing every year, or colonoscopy every 10 years. Additionally, stool DNA testing, also known as FIT-DNA testing, may be used to screen for colorectal cancer; however, the optimal screening interval is unclear. The American Cancer Society (ACS) recommends that stool DNA testing occur every 3 years. The ACS/U.S. Multi-Society Task Force/American College of Radiology colorectal cancer screening guideline recommends preference to cancer prevention tests (colonoscopy, flexible sigmoidoscopy, double contrast barium enema, or CT colonography) over cancer detection tests (gFOBT or FIT) when resources are available.

According to the USPSTF, flexible sigmoidoscopy every 10 years with gFOBT or FIT every year is an appropriate screening strategy. Randomized controlled trials have consistently demonstrated a mortality benefit for distal, but not proximal, colorectal cancer of 30% to 50% with flexible sigmoidoscopy.

In patients at average risk, colonoscopy can be performed every 10 years. Observational studies have shown that colonoscopy provides significant mortality benefit for both distal and proximal colorectal cancer. Colonoscopy is the preferred test of the American College of Gastroenterology.