Antibiotic use and risk of colorectal cancer: a systematic review and dose–response meta-analysis

Background It is understudied whether the posed association of oral antibiotics with colorectal cancer (CRC) varies between antibiotic spectrums, colorectal continuum, and if a non-linear dose-dependent relationship is present. Design Three electronic databases and a trial platform were searched for all relevant studies, from inception until February 2020, without restrictions. Random-effects meta-analyses provided pooled effect-sizes (ES) with 95% confidence intervals (CI). Dose–response analyses modelling the relationship between number of days exposed to antibiotics and CRC risk were extended to non-linear multivariable random-effects models. Results Of 6483 identified publications ten were eligible, including 4.1 million individuals and over 73,550 CRC cases. The pooled CRC risk was increased among individuals who ever-used antibiotics (ES = 1.17, 95%CI 1.05–1.30), particularly for broad-spectrum antibiotics (ES = 1.70, 95%CI 1.26–2.30), but not for narrow-spectrum antibiotic (ES = 1.11, 95% 0.93–1.32). The dose–response analysis did not provide strong evidence of any particular dose–response association, and the risk patterns were rather similar for colon and rectal cancer. Discussion The antibiotic use associated CRC risk seemingly differs between broad- and narrow-spectrum antibiotics, and possibly within the colorectal continuum. It remains unclear whether this association is causal, requiring more mechanistic studies and further clarification of drug–microbiome interactions.