Impact of antibiotic exposure on the risk of colorectal cancer.

Cancer Prevention/Epidemiology
Session Type and Session Title: 
General Poster Session, Cancer Prevention/Epidemiology
Abstract Number: 
J Clin Oncol 32:5s, 2014 (suppl; abstr 1599)
Shimon Ben Boursi, Kevin Haynes, Ronac Mamtani, Yu-Xiao Yang; Sheba Medical Center, Ramat Gan, Israel; Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA; Abramson Cancer Center of the University of Pennsylvania, Philadelphia, PA; Perelman School of Medicine at the University of Pennsylvania, philadelphia, PA

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Abstract Disclosures


Background: Previous reports revealed colonic dysbiosis in tumor tissue from cases with colorectal cancer (CRC) showing lower levels of microbial diversity and an enrichment of certain bacterial strains. It was suggested that the composition of the microbiota might serve, among other genetic and environmental factors, as a significant promoter of the multistep process of CRC formation. Antibiotic therapy reduces the overall bacterial diversity, with substantial consequences for the resultant functional stability of the colonic microbiota. Aim: To evaluate the association between the type and cumulative dose of antibiotic exposure and CRC risk. Methods: We conducted a nested case-control study using The Health Improvement Network (THIN), a large population-based medical records database from the United Kingdom (UK) that contains information on 11.7 million patients with follow up of up to 18 years. Study cases were defined as those with any medical code of CRC. Subjects with known familial colorectal cancer syndromes or IBD were excluded from the study. For every case, 4 eligible controls matched on age, sex, practice site, and duration of follow-up before index date were selected using incidence density sampling. Exposure was defined as any antibiotic therapy at least 6 month before index date. The OR and 95%CI were estimated using conditional logistic regression analysis adjusted for BMI, alcoholism, smoking history, Diabetes mellitus and chronic NSAIDs use. Results: 22,023 CRC patients and 85,981 controls were identified with a mean follow up time of 6 years (SD 3.53). The adjusted OR for CRC among user of penicillins, quinolones and metronidazole was 1.08 (95%CI 1.04-1.12), 1.08 (95%CI 1.03-1.14) and 1.11 (95%CI 1.05-1.18) respectively with p<0.0001 for all. The modest risk increase remained statistically significant only for remote exposure to penicillins (OR 1.05, 95%CI 1.001-1.09, for exposure 10 years before index date). There was no statistically significant effect with other antibiotic classes, anti-viral or anti-fungal therapy. Conclusions: Past exposure to Penicillins is related to a modest elevation in CRC risk, possibly through effects on the colonic microbiota.