562P Quantifying the effect of colonoscopy and polypectomy rates in stage shift of colorectal cancer and reduced need for adjuvant chemotherapy

Existing literature supports the principle of early detection of colorectal cancer (CRC) via screening but has not definitively demonstrated an association between colonoscopy or polypectomy rates and CRC stage over time. A longitudinal study was performed using the Australian national health database to obtain colonoscopy and polypectomy rates between 1998-2017. A second prospective database of CRC resection specimens was analysed for this period. The cohort was divided into three based on time intervals related to the national bowel cancer screening program: pre-commencement 1998-2006 (Period A), immediately post-commencement 2007-2011 (Period B), and subsequent years 2012-2017 (Period C). Annual colonoscopy rates doubled, and polypectomy rates tripled during the study (p<0.001). A total of 4506 patients underwent colorectal cancer resections. Annual colonoscopy rate correlated to a lower T-stage (p=0.038) and lower N-stage (p=0.026) leading to a 7% absolute (13.4% relative) increase in early CRC (stage I-II) in Period C (p<0.001). Across the study there was also a significant increase in right-sided tumours, and concurrent MMR deficiency and BRAF mutation. Polypectomy and colonoscopy rates increased after the introduction of a national screening program which correlated to a clinically relevant shift to earlier CRC stages, a reduction in CRC incidence which manifested five years after implementation, and a reduced need for adjuvant chemotherapy.