Lee JK, et al. - In this retrospective cohort study involving 1,251,318 study participants aged 50-75 years, researchers examined the long-term risks of colorectal cancer (CRC) and CRC-related deaths following colonoscopy with normal results (negative for CRC) in average-risk patients of a large community-based setting vs unscreened individuals. Compared with unscreened individuals, a negative colonoscopy result in average-risk patients was correlated with a lower risk of CRC and related deaths for > 12 years after examination. The authors suggested that these study findings may be able to inform guidelines for rescreening.

Methods

• This investigation was conducted in an integrated healthcare delivery organization serving > 4 million members across Northern California.
• Between January 1, 1998, and December 31, 2015, eligible patients were enrolled, and the study was completed on December 31, 2016.
• Screening was examined as a time-varying exposure.
• All study participants contributed person-time unscreened until they were either screened or censored.
• The participants contributed person-time in the negative colonoscopy results group until they were censored if the screening received was a negative colonoscopy result.
• The hazard ratios (HRs) for CRC and related deaths were calculated according to time since negative colonoscopy result (or since cohort entry for those unscreened) using Cox proportional hazards regression models, and were adjusted for age, sex, race/ethnicity, Charlson comorbidity score, and body mass index.

Results

• There was a 46% lower risk of CRC (hazard ratio, 0.54; 95% CI, 0.31-0.94) and 88% lower risk of related deaths (hazard ratio, 0.12; 95% CI, 0.02-0.82) at the current guideline-recommended 10-year rescreening interval among individuals with negative colonoscopy results vs unscreened individuals.