The effects of smoking on the risk of colorectal cancer.

Purpose: The aim of this study was to assess the effects of smoking on the risk of colorectal cancer according to anatomic subsite.

Methods: Between 1979 and 1985 a population-based case-control study of cancer at multiple sites was performed in Montréal, which accrued over 4,000 males in total, including cases of colorectal cancer, other cancers, and population controls. The present analysis was restricted to the 585 cases with histologically proven adenocarcinoma of the large bowel, aged 35 to 70 years, who underwent face-to-face interviews and provided adequate smoking histories.