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Fecal immunochemical testing (FIT) for stool hemoglobin is highly sensitive for colorectal cancer (CRC) but not for advanced adenomas (precursors for CRC). In observational studies, researchers found that FIT was more sensitive for detecting advanced adenomas in patients who routinely took low-dose aspirin than in patients who did not. In this study, researchers in Germany randomized more than 2000 patients (mean age, 60) scheduled for colonoscopy to single 300-mg doses of aspirin or placebo (excluding patients with recent use of aspirin or similar medications and prior CRC or rectal bleeding). Stool samples (collected on the second day after taking the study drug) were analyzed at two cutoff levels: 17 µg of hemoglobin per g of feces and 10.2 µg per g. Patients followed usual bowel preparation protocols and underwent colonoscopy within 3 months after recruitment.
Eight cases of CRC and 216 advanced adenomas were detected via colonoscopy. At both cutoff levels, FIT sensitivity for advanced adenoma was not significantly better in patients who received aspirin than in controls. At the higher cutoff, sensitivities were 28.6% with aspirin and 22.5% with placebo. At the lower cutoff, sensitivities were 40.2% with aspirin and 30.4% with placebo. Results were similar in men and women.
Brenner H et al. Effect of a single aspirin dose prior to fecal immunochemical testing on test sensitivity for detecting advanced colorectal neoplasms: A randomized clinical trial. JAMA 2019 May 7; 321:1686. (https://doi.org/10.1001/jama.2019.4755)
Comment
These results conflict with findings in observational studies. A larger study might have shown statistical significance, albeit with small differences. The authors note that even small differences could be clinically useful given the low risk and low cost of a single dose of aspirin. For now, giving aspirin to enhance the sensitivity of FIT cannot be recommended. But for patients who already are taking daily aspirin, a U.S. multisociety guideline does not recommend stopping aspirin before FIT (Am J Gastroenterol 2017; 112:37).