Occupational Asbestos Exposure and Incidence of Colon and Rectal Cancers in French Men: The Asbestos-Related Diseases Cohort (ARDCo-Nut)

Background: Despite numerous studies, the relationships between asbestos exposure and colo-rectal cancer still remain controversial.

Objectives: To examine the association between asbestos exposure and colo-rectal cancer occurence.

Methods: Volunteered retired workers previously occupationally exposed to asbestos were invited to participate in ARDCo screening program for asbestos-related diseases between October 2003 and December 2005 in four French regions. A 10-year follow-up study was conducted in 14,515 male subjects, and additional data on risk factors for colo-rectal cancer were collected from the ARDCo-NUT subsample of 3,769 subjects in 2011. Annual determination of eligible subjects for free medical care because of colo-rectal cancer was carried out until 2014. Survival regression based on the Cox model was used to estimate the risk of colo-rectal cancer, with age as the main time variable in relation to the time since first exposure (TSFE) and cumulative exposure index (CEI) to asbestos, and with adjustment for smoking in the overall cohort and for smoking, nutritional and personal risk factors for these cancers in ARDCo-NUT subsample.

Results: In the overall cohort, a significant dose-response relationship was observed between CEI to asbestos (Hazard Risk (HR)=1.104[1.01-1.21]), TSFE (20 and <40 years; HR=4.53 [7.86-11.04]) and colon cancer incidence, after adjustment for smoking. Using stratified analysis on TSFE, a stronger relationship was observed for TSFE<40 years (HR=1.57[1.25-1.98]). Analyses on ARDCo-NUT subsample confirmed this association only in TSFE<40 years strata, after adjustment for smoking, and other risk factors for colon cancer. No association with rectal cancer was observed.

Conclusions: This study supports an association between occupational exposure to asbestos and colon cancer incidence.

Keywords: cohort, asbestos, incidence, survival regression, colo-rectal cancer