SO-25 Global rise in early-onset colorectal cancer: An association with antibiotic consumption?

Abstract

Background: Since the late 1980s, global antibiotic consumption and colorectal cancer (CRC) rates in those aged less than 50 years have soared. As the gut micro-biome modulates many human processes, significantly altering microbiome structure and diversity with antibiotic therapy has previously been shown to influence CRC genesis in older adults. To our knowledge, no study before has investigated antibiotic usage in early-onset CRC (EOCRC). This study will investigate the association between exposure to antibiotics and risk of EOCRC predisposition, and also evaluate antibiotic usage in older adults with CRC for comparison. Methods: A nested case-control study was conducted using Scottish primary care data. CRC cases, diagnosed between 1999 to 2011, were identified from GP records and matched with up to 5 controls. Analyses were conducted separately in EOCRC cases (diagnosed ¼50 years). Prescriptions for oral antibiotics (by drug class and by anaerobic/non-anaerobic effect) were extracted and total antibiotic exposure period determined for each matched set. Total exposure time in days was categorised into 0, 1-15, 16-60, and >60 days. Cases and controls were described and conditional logistic regression used to calculate odds ratios (OR) and 95% confidence intervals (CI) for the associations between each exposure and CRC (by tumour location), adjusting for comorbidities. Test for trend was used to evaluate any exposure-response relationship.