Smoking and other risk factors associated with the stage and age of diagnosis of colon and rectum cancers.

The present study analyzes data on colon and rectum cancer cases from a population-based cancer registry to determine the effect of smoking, alcohol drinking, and family history of cancer on disease characteristics. A total of 771 cases of primary invasive cancer of the colon and 304 cancers of the rectum constitute the study sample. More advanced colon cancer was present in female smokers than in female nonsmokers, while in males there was no smoking effect on stage at diagnosis of colon cancer. For cancer of the rectum, male smokers had a higher frequency of advanced disease than did nonsmokers. Smoking men and women were found to have lower mean ages at diagnosis of both colon and rectum cancer than did nonsmokers (p less than 0.001 and p less than 0.004, respectively). Alcohol drinking remained consistently associated with lower age at diagnosis in both sexes for both colon and rectum cancer (p less than 0.001 and p less than 0.001, respectively). Those cases of rectum cancer having positive family history for colorectal cancer in their first degree relatives had younger age at diagnosis than those having negative family history (p less than 0.005). The age at diagnosis was progressively younger as the number of risk factors increased (p less than 0.001 for colon cancer and p less than 0.003 for cancer of the rectum). Our findings indicate an interaction between exposures to risk factors that are potentially carcinogenic or cocarcinogenic and manifestations of cancer of the colon and rectum.