Long-term effect of eradication on colorectal cancer incidences

Background: There is evidence supporting the association between Helicobacter pylori infection and colorectal cancer (CRC), but whether H. pylori eradication reduces the risk of CRC is still unknown. Objectives: To compare the incidence of CRC in subjects who had received H. pylori eradication therapy with general population. Design: A population-based retrospective cohort study. Methods: This study included all H. pylori -infected subjects who had received their first course of clarithromycin-containing triple therapy in 2003–2015 in Hong Kong. We compared the observed incidences of CRC in this H. pylori eradicated cohort with the expected incidences in the age- and sex-matched general population. The standardized incidence ratio (SIR) with 95% confidence interval (CI) was computed. Results: Among 96,572 H. pylori -eradicated subjects with a median follow-up of 9.7 years, 1417 (1.5%) developed CRC. Primary analysis showed no significant difference in the observed and expected incidences of CRC (SIR: 1.03, 95% CI: 0.97–1.09). However, when stratified according to the follow-up period, higher incidence of CRC was only observed in the first 5 years after eradication (SIR: 1.47, 95% CI: 1.39–1.55), but it was lower (SIR: 0.85, 95% CI: 0.74–0.99) than general population after 11 years. When stratified by tumor location, the observed incidence was higher for colon (SIR: 1.20, 95% CI: 1.12–1.29) but lower for rectal cancer (SIR: 0.90, 95% CI: 0.81–0.999) among H. pylori -eradicated subjects. Conclusions: H. pylori -infected subjects appeared to have a higher incidence of CRC initially, which declined progressively to a level lower than general population 10 years after H. pylori eradication, particularly for rectal cancer.