Phenotypes of lung cancer and statistical interactions between tobacco smoking and occupational exposure to asbestos and crystalline silica from a large case-only study: The CaProMat study

Abstract

Objectives: The aim of this study was to assess the effect modification of the association between tobacco smoking and phenotypes of lung cancer (histological type, tumor location, and age at diagnosis) by occupational exposure to asbestos or to crystalline silica.

Materials and methods: The CaProMat study is a pooled case-only study including 7256 male lung cancer cases recruited between 1996 and 2011 in France and Canada. Two job-exposure matrices (JEMs) were used to assess occupational exposure to asbestos and crystalline silica. Statistical interactions between tobacco smoking and occupational exposure to asbestos or crystalline silica were assessed using unconditional logistic regression models for histological type and tumor location and linear regression models for age at diagnosis.

Results: Tobacco smoking was associated with squamous cell carcinoma and small cell carcinomas as well as an earlier age at diagnosis. Additional exposure to either asbestos or crystalline silica did not modify the effect of tobacco smoking for either histological type or age at diagnosis. Neither tobacco smoking nor occupational exposure to asbestos or crystalline silica influenced tumor location.

Conclusions: Tobacco smoking was the main factor related to histological type and age at diagnosis. Those associations were not modified by occupational exposure to asbestos or crystalline silica.

Keywords: Asbestos; Crystalline silica; Interaction; Lung cancer; Occupational exposures; Tobacco smoking.