Increased Colorectal Cancer Observed Among Asbestos Exposed Workers

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Does asbestos exposure cause colorectal cancer? This remains in dispute. The CARET study – a failed attempt to demonstrate chemoprevention of lung cancer by Vitamin A – provides information. Bottom line, asbestos exposed workers suffered increased colorectal cancer. The findings are limited to heavy smokers because only heavy smokers were permitted in the study.


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Am J Epidemiol. 2005 Sep 21; [Epub ahead of print]

Evidence for Excess Colorectal Cancer Incidence among Asbestos-exposed Men in the Beta-Carotene and Retinol Efficacy Trial.

Aliyu OA, Cullen MR, Barnett MJ, Balmes JR, Cartmel B, Redlich CA, Brodkin CA, Barnhart S, Rosenstock L, Israel L, Goodman GE, Thornquist MD, Omenn GS.Yale Occupational and Environmental Medicine Program and the Cancer Center, Yale University School of Medicine, New Haven, CT.The relation between asbestos exposure and colorectal cancer remains controversial. The authors of this 1984-2004 US study examined the association among 3,897 occupationally exposed participants in the Beta-Carotene and Retinol Efficacy Trial (CARET) for chemoprevention of lung cancer, followed prospectively for 10-18 years. When a Cox stratified proportional hazards model was used, risks of colorectal cancer were elevated among male heavy smokers exposed to asbestos. Their relative risk was 1.36 (95% confidence interval: 0.96, 1.93) when compared with that for CARET heavy smokers not exposed to asbestos, after adjusting for age, smoking history, and intervention arm. The presence of asbestos-induced pleural plaques at baseline was associated with a relative risk of 1.54 (95% confidence interval: 0.99, 2.40); colorectal cancer risk also increased with worsening pulmonary asbestosis (p = 0.03 for trend). A dose-response trend based on years of asbestos exposure was less evident. Nonetheless, these data suggest that colorectal cancer risk is elevated among men occupationally exposed to asbestos, especially those with evidence of nonmalignant asbestos-associated radiographic changes.