Writing in the August issue of the journal Diseases of the Colon and Rectum, researchers conducted a populations-based case-control study between 1979 and 1985 at several medical centers in Montréal, Canada.
The study population, which totaled over 4,000 males, included cases of colorectal cancer, other cancers, and population controls.
The analysis was restricted to the 585 cases with histologically proven adenocarcinoma of the large bowel.
All patients within this group were aged between 35 and 70 years, and underwent face-to-face interviews where they provided adequate information on their smoking histories.
| Cigar, but not cigarette smoking related to colorectal cancer rates |
| Diseases of the Colon and Rectum |
Of these 585 patients, 179 suffered from cancer in the proximal colon, 179 had cancer in the distal colon, and 230 had colorectal cancer.
The control population consisted of 405 cancer controls, whose tumor types were considered unrelated to smoking, and 505 population controls.
Upon examination of the data, the researches were able to identify a positive association between cigar smoking and cancer of the rectum.
They also found some suggestion of a weak positive association between cigarette smoking and cancer of the proximal colon.
In addition, there was evidence of an inverse relationship between cigarette smoking and cancer of the distal colon, although neither of these associations was statistically significant.
The research group found no link between cigarette smoking and incidence of rectal cancer.
Commenting on the findings of the study, Dr Colin R. Sharpe, of L'Institut National de la Recherche Scientifique-Institut Armand-Frappier, at Université du Québec in Laval, Canada, said, "Cigar smoking seems to be associated with the development of rectal cancer."
"If the positive association between cigarette smoking and cancer of the proximal colon is real, it might partially explain the proximal shift in the anatomic distribution of colorectal cancer that has been observed, because of the increasing prevalence of cigarette smoking during the middle of the 20th century."