127 Physical harm resulting from colorectal cancer screening – a systematic review

Objectives Screening for cancer intends to provide benefit but also entails an unintended risk of causing harm. Many types of harm might occur during the screening cascade, including the risk of overdiagnosis due to both overdetection and overdefinition. Regardless of the diagnostic outcome, all screening participants are at risk of enduring physical harms due to screening. Harms of screening are often underreported and asymmetrically presented compared to the benefits of screening. In addition, the definition, measurement and reporting of harms is heterogeneous and of poor quality in clinical studies. These methodological issues have major consequences when systematic reviews do not focus sufficiently on harm assessment methods in studies. As former reviews of colorectal cancer screening have not addressed the above detailed issues, this systematic reviews aims to assess the evidence regarding physical harms of colorectal cancer screening in line with recent methodological recommendations in the PRISMA harms extension. Method Conduct and reporting follows recommendations from the PRISMA harms extension and the Cochrane Handbook. The study protocol was published on PROSPERO prior to data extraction to ensure transparency. Databases were searched in April 2017 and included Pubmed, Medline, Embase, Cinahl, PsycInfo and the Cochrane library. There were no restrictions concerning study design, language or date of publication. All types of clinical studies were included if they provided data on physical harms due to screening of asymptomatic individuals in average risk of colorectal cancer by any combination of fecal occult blood testing, sigmoidoscopy and/or colonoscopy. Using an extended version of the newly published risk of bias tool for non-randomized studies, ROBINS-I by the Cochrane Collaboration, we appraised the risk of bias of the included studies. The overall quality of the evidence will be evaluated using the GRADE criteria. The study protocol is available at: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=58844 Results Preliminary results and methodological issues identified in studies included for review will be presented at the conference.