An association between antibiotic use and the risk of cancer

B116

Background:
 >Antibiotic use has been hypothesized to be associated with the risk of cancer but the evidence is sparse and inconsistent. The aim of the study was to determine whether antibiotic use predicts the development of various cancers.
 >Methods:
 >A nationwide cohort study included 3,112,624 individuals with no history of cancer. Information on their antibiotic use between 1995 and 1997 was obtained from the Drug Prescription Registry. During the period 1998-2004, 134,070 cancer cases were ascertained from the Finnish Cancer Registry. Cox proportional hazards regression was used to estimate the relative risks (RRs) with 95 percent confidence intervals (95% CIs).
 >Results:
 >Antibiotic use was associated with an increased risk of cancer: for categories of increasing antibiotic use (0-1, 2-5, and ≥ 6 prescriptions), RRs (95% CIs) for cancer were 1.0 (reference), 1.27 (1.26 to 1.29) and 1.37 (1.34 to 1.40). RRs (for comparison of lowest and highest exposure group) for the most common primary sites ie. prostate, breast, lung and colon were 1.39 (1.31 to 1.48), 1.14 (1.09 to 1.20), 1.79 (1.67 to 1.92), and 1.14 (1.04 to 1.26), respectively. RRs for other primary sites varied between 0.90 (0.76-1.05) for ovary to 2.60 (1.60-4.20) for endocrine gland (excluding thyroid).
 >Conclusions: Antibiotic use predicts an increased risk of cancer. The design of our study does not permit us to determine whether antibiotic use is causally related to cancer or whether there are some other factors to explain our findings. Our results do not give ground for any recommendation on antibiotic use but further research is required.