Lead Time Bias May Contribute to the Shorter Life Expectancy in Post-colonoscopy Colorectal Cancer

Background The long-term outcomes of post-colonoscopy colorectal cancer have varied in previous studies. Our nationwide cohort analysis estimated expected years of life lost to adjust for lead time bias. Aim We recalculated the long-term outcomes for post-colonoscopy and detected colorectal cancer. Methods Patients with colorectal cancer registered in the Taiwan Cancer Registry between 2002 and 2009 were enrolled. The detected group included 22,169 cases of colorectal cancer confirmed within 6 months after a colonoscopy. The post-colonoscopy group included 1653 cancer patients who received a colonoscopy 6–60 months before diagnosis. Patients were followed up until 2011. We simulated age-, sex-, and calendar year-matched referents from life tables in the Taiwan National Vital Statistics using a Monte Carlo method. The life expectancy and expected years of life lost of the cancer patients were obtained from extrapolation of the logit transformation of the survival ratio between the cancer cohorts and the referent groups. Results Post-colonoscopy colorectal cancer had shorter life expectancies than detected cancer (stages 2–4: 13.6 vs. 16.1 years; 8.7 vs. 12.6 years; 2.1 vs. 4.1 years, p