Women who smoke appear to have nearly twice the risk of developing rectal cancer compared with women who never smoked cigarettes, which supports the accumulating evidence of this relationship, researchers report.

The risk of rectal cancer among women increased along with the number of cigarettes they smoked per day, longer smoking duration, and older age at smoking cessation, findings that also support evidence from earlier studies, Dr. Electra D. Paskett, and colleagues report in the Journal of the National Cancer Institute.

“Smoking cessation and prevention are yet another way to prevent colorectal cancer,” Paskett, of Ohio State University, in Columbus, told Reuters Health. Women who choose to continue smoking should receive regular screening for colorectal cancer, Paskett added.

The investigators looked at the incidence of colorectal cancer among more than 140,000 women between 50 and 79 years old, who participated in Women’s Health Initiative, a long-term observational study.

Of these women, 51 percent reported never smoking, 42 percent were past smokers, and 7 percent were current smokers.

Over 7.8 years, on average, 1,242 of the women developed invasive colorectal cancer, the researchers found. Of these cancers, 176 were rectal cancer.

Compared with women who never smoked, current smokers were 95 percent more likely to develop rectal cancer, but did not have an increased risk of colon cancer. These relationships held after the researchers adjusted the data to account for other factors known to influence colorectal cancer development.

These factors included age, ethnicity, family history, physical activity; nonsteroidal anti-inflammatory drugs, hormone therapy; alcohol use; dietary intake of calcium, fiber, fat and red meat; waist circumference; and the women’s history of diabetes.

A similar analysis did not associate passive smoking with an increased risk for colorectal cancer, the investigators note.

As mentioned, these findings provide another reason to encourage smoking prevention and cessation programs, the investigators conclude.

SOURCE: Journal of the National Cancer Institute, November 13, 2007.