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Effects of oral anticoagulants and aspirin on fecal tests in colorectal cancer screening

A fecal immunochemical test for occult blood is the most frequently used colorectal cancer screening tool worldwide. It is recommended that a positive fecal immunochemical test (FIT) be followed by colonoscopy. A high positive predictive value is important in a screening program to reduce the number of unnecessary colonoscopies. Aspirin and anticoagulants, which are associated with gastrointestinal bleeding, are common medications used by the target population for colorectal screening, patients 50 years and older. According to current screening guidelines, discontinuing antithrombotic treatment prior to fecal sampling is not recommended. The authors conducted a study to assess the impact of aspirin, warfarin, and direct-acting oral anticoagulants (DOACs) on the positive predictive value for colorectal cancer and advanced adenoma following a positive FIT result. They used data from a large colorectal cancer screening trial in Norway. The participants were 50 to 74 years old and had a positive FIT result and subsequent colonoscopy. The subjects who used regular aspirin, warfarin, or DOACs were defined as users. Nonusers served as controls. The primary outcomes were the positive predic-tive value for colorectal cancer and advanced adenoma. Among 5,908 participants, the positive predictive value for colorectal cancer was 3.8 percent for aspirin users versus 6.4 percent for matched nonusers (P = .006), while the positive predictive value for advanced adenoma was 27.2 percent for aspirin users versus 32.6 percent for matched nonusers (P = .011). The positive predictive value for colorectal cancer was 0.9 percent for DOAC users versus 6.8 percent for matched nonusers (P = .001), while the positive predictive value for advanced adenoma was 20.5 percent for DOAC users versus 32.4 percent for matched nonusers (P = .002). There was no significant difference in positive predictive values for colorectal cancer or advanced adenoma in warfarin users compared with nonusers. To the authors’ knowledge, this is the largest cohort of aspirin and DOAC users to be studied for FIT performance. The authors concluded that aspirin and DOAC users have a lower positive predictive value for colorectal cancers and advanced adenomas compared with nonusers. They noted that although aspirin and DOAC use increases the rate of false-positive tests, a pause in taking these drugs may increase the risk of potentially life-threatening or disabling thromboembolic and cardiovascular events. Requiring medication adjustment may also complicate FIT screening and impact adherence to the screening program. The authors suggested that a possible approach to this problem may be to repeat FIT testing for those on DOACs who have a positive FIT result.

Randel KR, Botteri E, Romstad KMK, et al. Effects of oral anticoagulants and aspirin on performance of fecal immunochemical tests in colorectal cancer screening. Gastroenterology. 2019. https://doi.org/10.1053/j.gastro.2019.01.040.

Correspondence: Dr. Kristin Ranheim Randel at kristin.ranheim.randel@cancerregistry.no