Smoking a Significant Risk Factor for Colorectal Polyps

SEATTLE—Cigarette smoking appears to be a significant risk factor for colon polyps, equal to a family history of colon cancer, according to Rajeev Attam, MD, a senior fellow in the Division of Gastroenterology, Stony Brook University School of Medicine, New York. In a large colon cancer screening study, approximately 19% of ex-smokers and 17% of nonsmokers had polyps, compared with 25% of current smokers.

Dr. Attam, who presented the results during the President’s Plenary Session of the 67th Annual Scientific Meeting of the American College of Gastroenterology (abstract 5), called smoking a key risk factor for colorectal polyps. He suggested that physicians may consider performing screening colonoscopies in current smokers before the age of 50, the standard age for average-risk individuals.

Dr. Attam and his colleagues evaluated 1,041 nonsmokers, 338 smokers (smoked more than 10 pack-years), and 371 ex-smokers (quit smoking more than 10 years ago and smoked more than 10 pack-years) who had undergone screening colonoscopy between December 1999 and April 2002. Subjects were also assessed for age, sex, body mass index, family history of colorectal neoplasia, ethni-city, socioeconomic status, alcohol use, daily exercise, daily NSAID use, and dietary patterns such as consumption of fruits and vegetables.

"Smokers had a much higher prevalence of colorectal neoplasia, compared with nonsmokers," Dr. Attam said. "There was no significant difference in prevalence between nonsmokers and ex-smokers." Smokers also had a higher prevalence of significant left-sided neoplasia, compared with nonsmokers.

Significant colorectal neoplasias were defined as more than two polyps, polyps larger than 1 cm, and villous or high-grade dysplasia. Using multivariate analysis, the only significant predictive factors for this type of lesion were age over 60 years and a history of smoking. Significant colorectal dysplasias were found in 13% of smokers, 8% of ex-smokers, and only 7% of nonsmokers.

Female sex and drinking wine appeared to lower the risk of polyps overall, as did quitting tobacco for more than 10 years. Body mass index, weekly exercise, daily NSAID use, and consumption of fruits and vegetables did not appear to be predictive of colorectal polyps.

Smokers should be considered as high risk, similar to individuals with a family history of colon cancer, and smokers may need to be screened at an earlier age, Dr. Attam concluded. "On the basis of our findings," he said, "smokers may benefit from periodic flexible sigmoidoscopies between colonoscopies."

A Modifiable Risk Factor

In an interview, lead investigator Joseph Anderson, MD, said that "the main message from our study is the importance of risk factors other than the traditional ones that we usually look at, such as age and family history. Our study is the first screening study to examine multiple potential colorectal cancer risk factors." Dr. Anderson is assistant professor of medicine, Division of Gastroenterology, Stony Brook University School of Medicine.

The study also heightens the role that the physician can play in helping a patient reduce certain risk factors. "When a gastroenterologist sees a patient, his obligation is not only to screen for problems such as polyps but also to potentially counsel the patients about risk factors that are controllable," he said.

Traditional risk factors, such as family history and age, are not within the realm of a patient’s control, he explained, but "risk factors such as smoking, along with others that may be identifiable in the future from other studies, can indeed be modified by the patient."

He suggested that the gastroenterologist should play a role in counseling patients about modifiable risk factors. "Perhaps the gastroenterologist can also be on the front line, along with the internist and pulmonologist, to help patients stop smoking," Dr. Anderson said.