Is antibiotics use really associated with increased risk of colorectal cancer? An updated systematic review and meta-analysis of observational studies.

Purpose: The association between antibiotics and colorectal cancer (CRC) risk has drawn increasing attention but remains controversial. This study was performed to clarify the association.

Methods: A systematic review and meta-analysis was performed on seven electronic databases. The pooled odds ratios (OR) with a 95% confidence interval (CI) were calculated to estimate the association using the fixed-effects model or the random-effects model.

Results: Ten studies that contained 4,853,289 participants were included in our study. We found that antibiotics use was associated with a higher risk of CRC (OR 1.09, 95%CI 1.02-1.17, I = 92.8%). More than 60 days of antibiotics use and 5 prescriptions of antibiotics were significantly associated with a higher risk of CRC. Sub-analysis on different types of antibiotics found that anti-anaerobic antibiotics, penicillins, and quinolones use led to increased risk of CRC (OR 1.22, 95% CI 1.04-1.44, I = 89.1%; OR 1.09, 95% CI 1.04-1.13, I = 69.2%; OR 1.15, 95% CI 1.03-1.35, I = 88.2%; respectively) and colon cancer (OR 1.28, 95% CI 1.04-1.58, I = 98.5%; OR 1.09, 95% CI 1.05-1.12, I = 0; OR 1.09, 95% CI 1.04-1.15, I = 0; respectively). However, antibiotics use was not significantly associated with rectal cancer (OR 1.03, 95% CI 0.92-1.16, I = 77.6%).

Conclusion: It needs attention that antibiotics use is associated with a higher risk of CRC, especially for colon cancer. Clinicians should be aware of the potential risk of CRC when prescribing anti-anaerobic antibiotics, penicillins, and quinolones in the future. Further studies are needed to assess any potential differences by tumor sites and class of antibiotics.