Association Between Colorectal Cancer Mortality and Gradient Fecal Hemoglobin Concentration in Colonoscopy Noncompliers

Background: To what extent the risk for colorectal cancer (CRC) death among noncompliers of colonoscopy is elevated following positive fecal immunological testing and whether the elevated risk varies with the fecal hemoglobin concentration (f-Hb) and location of CRC have not been researched. Methods: We used data on 59 389 individuals (4.0%) among 1 489 937 Taiwanese screenees age 50 to 69 years with f-Hb 20 μg hemoglobin or more per gram of feces from 2004 to 2009. They were classified into 41 995 who received colonoscopy and 10 778 who received no confirmatory examination; the latter was categorized into three risk groups according to f-Hb (20-49, 50-99, and 100+). Mortality from CRC as the primary end point was monitored until December 31, 2012. Results: A 1.64-fold (95% confidence interval [CI] = 1.32 to 2.04) increased risk for CRC death for the noncolonoscopy group as opposed to the colonoscopy group adjusting for differences in baseline characteristics. A gradient relationship was noted between cumulative mortality and age- and sex-adjusted f-Hb categories with 1.31-fold (95% CI = 1.04 to 1.71), 2.21-fold (95% CI = 1.55 to 3.34), and 2.53-fold (95% CI = 1.95 to 3.43) increased risk, respectively, for the 20-49, 50-99, and 100+ risk groups in the noncolonoscopy group compared with the colonoscopy group. The noncolonoscopy group led to a statistically significant 1.75-fold increased risk (95% CI = 1.35 to 2.33) for CRC of the distal colon but a statistically nonsignificant 1.11-fold increased risk (95% CI = 0.70 to 1.75) for the proximal colon, compared with the colonoscopy group. When the comparator was limited to subjects whose colonoscopy was completed to the cecum, the statistically significantly elevated risk for CRC mortality was seen for both distal and proximal colon in the noncolonoscopy group. Conclusions: After a positive fecal immunochemical test, colonoscopy can reduce by about half the number of deaths from CRC. Among colonoscopy noncompliers, higher f-Hb is associated with an increased risk of mortality from CRC in a dose-response manner.