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

Our plain-English summary of Occupational Asbestos Exposure and Incidence of Colon and Rectal Cancers in French Men: The Asbestos-Related Diseases Cohort (ARDCo-Nut), by C. Paris, I. Thaon, F. Hérin, et al (Environmental Health Perspectives, 2017).

The study

• Authors: C. Paris, I. Thaon, F. Hérin, B. Clin, A. Lacourt, A. Luc, G. Coureau, P. Brochard, S. Chamming's, A. Gislard, P. Galan, S. Hercberg, P. Wild, J.C. Pairon, P. Andujar
• Journal: Environmental Health Perspectives
• Published: 2017;125(3):409-415
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: The relationships between asbestos exposure and colorectal cancer remain controversial.

Objectives: We examined the association between asbestos exposure and colorectal cancer incidence.

Methods: Volunteer retired workers previously exposed to asbestos were invited to participate in the French ARDCo screening program between 2003 and 2005. Additional data on risk factors for colorectal cancer were collected from the ARDCo-Nut subsample of 3,769 participants in 2011. Cases of colon and rectal cancer were ascertained each year through 2014 based on eligibility for free medical care following a cancer diagnosis. Survival regression based on the Cox model was used to estimate the relative risk of colon and rectal cancer separately, 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, and certain risk factors for these cancers in the ARDCo-Nut subsample.

Results: Mean follow-up was 10.2 years among 14,515 men, including 181 colon cancer and 62 rectal cancer cases (41 and 17, respectively, in the ARDCo-Nut subsample). In the overall cohort, after adjusting for smoking, colon cancer was significantly associated with cumulative exposure (HR = 1.14; 95% CI: 1.04, 1.26 for a 1-unit increase in ln-CEI) and ≥ 20-40 years since first exposure (HR = 4.67; 95% CI: 1.92, 11.46 vs. 0-20 years TSFE), and inversely associated with 60 years TSFE (HR = 0.26; 95% CI: 0.10, 0.70). Although rectal cancer was also associated with TSFE 20-40 years (HR = 4.57; 95% CI: 1.14, 18.27), it was not associated with ln-CEI, but these findings must be interpreted cautiously due to the small number of cases.

Conclusions: Our findings provide support for an association between occupational exposure to asbestos and colon cancer incidence in men. Citation: Paris C, Thaon I, Hérin F, Clin B, Lacourt A, Luc A, Coureau G, Brochard P, Chamming's S, Gislard A, Galan P, Hercberg S, Wild P, Pairon JC, Andujar P. 2017. Occupational asbestos exposure and incidence of colon and rectal cancers in French men: the Asbestos-Related Diseases Cohort (ARDCo-Nut). Environ Health Perspect 125:409-415; http://dx.doi.org/10.1289/EHP153.

In plain English

This cohort study followed 14,515 retired or unemployed French men who volunteered for asbestos screening in four French regions in 2003 to 2005; 656 (4.5%) were classified as not exposed. An industrial hygienist estimated each man's cumulative exposure from his work history, without air measurements; the cohort's fiber types are not given. National Health Insurance records to April 2014 showed 181 colon and 62 rectal cancers. Adjusted for smoking and time since first exposure, colon cancer was associated with higher cumulative exposure (HR = 1.14, 95% CI 1.04 to 1.26, per one-unit step on a log scale of exposure). This appeared only in men first exposed less than 40 years earlier. Colon and rectal cancer hazard ratios were higher at 20 to 40 years since first exposure than at 0 to 20 years. Rectal cancer was not associated with cumulative exposure. In a subgroup of 3,579 men with data on diet, weight and family history, no overall association with cumulative exposure appeared. The authors concluded the study supports an association between asbestos exposure and colon cancer, but urged caution on rectal cancer given few cases.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Prospective cohort study (about 10 years of follow-up) analysed with Cox proportional hazard models, with a subsample that answered a 2011 questionnaire on other colorectal cancer risk factors
• Who was studied: 14,515 men in the French Asbestos-Related Diseases Cohort (ARDCo). They were retired or unemployed volunteers recruited as previously occupationally exposed workers and were enrolled between October 2003 and December 2005 in four regions of France (Haute-Normandie, Basse-Normandie, Aquitaine, Rhône-Alpes). Table 1 classifies 656 of them (4.5%) as not exposed. Of the 14,515, 3,579 completed the 2011 ARDCo-Nut questionnaire.
• Exposure: Occupational asbestos exposure in sectors such as iron and steel manufacturing, construction, cargo handling, metalworking and ship repair. The article does not specify the fiber types to which cohort members were exposed. An industrial hygienist coded each job from work histories. A cumulative exposure index (exposure units times years) was calculated using intensity weights: low or passive 0.01, intermediate 0.1, high intermediate 1.0, high 10.0. Time since first exposure was also studied. No air measurements were available.
• Main results:
  • Whole cohort, colon cancer (181 cases), adjusted for smoking and time since first exposure: hazard ratio 1.14 (95% CI 1.04 to 1.26) for each 1-unit increase in ln(CEI + 1). The authors note this positive association was seen only after adjusting for time since first exposure and smoking.
  • Whole cohort, colon cancer, adjusted for smoking: 20 to 40 years since first exposure, compared with 0 to 20 years, HR = 4.67 (95% CI 1.92 to 11.46). 60 or more years since first exposure: HR = 0.26 (95% CI 0.10 to 0.70), an inverse association.
  • Whole cohort, colon cancer, by time since first exposure and adjusted for smoking. Men first exposed less than 40 years before: HR 1.57 (95% CI 1.25 to 1.98) per 1-unit increase in ln(CEI + 1), based on 1,166 observations and 25 cases. Men first exposed 40 or more years before: HR 1.05 (95% CI 0.95 to 1.16), based on 13,349 observations and 156 cases, no association.
  • Whole cohort, rectal cancer (62 cases), adjusted for smoking: 20 to 40 years since first exposure, compared with 0 to 20 years, HR = 4.57 (95% CI 1.14 to 18.27). No association with cumulative exposure.
  • ARDCo-Nut subsample (41 colon, 17 rectal cancers), adjusted for other risk factors: no association between cumulative exposure and colon or rectal cancer.
  • ARDCo-Nut subsample, colon cancer, men first exposed less than 40 years before: HR 1.94 (95% CI 1.23 to 3.07) per 1-unit increase in ln(CEI + 1), based on 264 observations and 5 cases.
• The authors' conclusion: The authors concluded that, together with earlier studies and limited experimental data, their study supports an association between asbestos exposure and colon cancer. They found no clear evidence of an association with rectal cancer and said that finding should be read cautiously because of the small number of cases.
• Limitations the authors state:
  • Participants were a selected population of male volunteers.
  • Exposure was assessed retrospectively, without air measurements.
  • The ARDCo-Nut subsample was small, which limited some analyses.
  • Many cancer cases were diagnosed before the 2011 questionnaire or did not respond to it. The effect of self-selection, loss to follow-up and non-response is hard to predict.
  • Rectal cancer cases were few compared with colon cancer cases.
  • Diagnoses came from insurance records. In areas with cancer registries, 39 of 44 insurance-recorded cases were confirmed in the registries.
  • Residual confounding cannot be ruled out.
  • The effect of less than 20 years since first exposure could not be tested.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Colon cancer.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Colorectal Cancer, Relative Risk, Cumulative Exposure, Occupational Exposure.

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• Identification of occupational cancer risks in British Columbia, Canada: a population-based case-control study of 1,155 cases of colon cancer — R. Fang, N. Le, et al. (2011)
• Digestive cancers and occupational asbestos exposure: incidence study in a cohort of asbestos plant workers — M. Boulanger, F. Morlais, et al. (2015)
• Asbestos exposure and neoplasia — I.J. Selikoff, J. Churg, et al. (1964)

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