Smoking habits independently predict colorectal polyps

Researchers found that smoking duration is independently correlated with colorectal polyps, and the association is highest with distal and serrated lesions, according to a new study published in the Journal of Clinical Gastroenterology.

Smoking is acknowledged as an established risk factor for a number of cancer types, including colorectal cancer (CRC), the third most common cancer type in the United States. The disease graduates from precursor polyps over time, allowing for possible prevention through screening interventions and surveillance.

“Current CRC screening and postpolypectomy surveillance guidelines are based on age, personal or familial history of CRC, and inflammatory bowel disease,” wrote the researchers, led by Naomi Fliss-Isakov, PhD, Department of Gastroenterology, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. “The addition of lifestyle risk factors like smoking to CRC risk stratification has been suggested; however, it has yet been incorporated into guidelines.”

Tobacco is the leading modifiable risk factor for various types of cancer and chronic illness. Experts estimate that smokers inhale more than 4,500 chemicals that can cause inflammation and genetic alteration.

Although a multifactorial model predicted smoking to be the greatest risk factor for CRC in a Western average-risk population, few studies have assessed whether smoking intensity and duration are specifically associated with CRC. In this study, the researchers examined whether lifetime smoking habits are associated with different polyps.

This case-control study included 828 consecutive participants aged 40-70 years who were undergoing screening or diagnostic colonoscopy. None of the patients had diabetes or were at high risk for CRC. The researchers defined control participants as those free of past or present polyps, and defined cases as those with a finding of any colorectal polyp. The team characterized polyps as either serrated or adenomatous. They recorded body measurements and conducted a medical and lifestyle interview for all study participants.

The researchers employed multivariate logistic regression to assess the association between smoking and different types of colorectal polyps, while adjusting for potential confounders including lifestyle factors and body mass index. They found that 17.8% of all participants were current smokers and 37.3% were past smokers. Past smokers had an average of 16 years since quitting.

The investigators found that current smoking, past smoking, and smoking intensity were associated with CRC, after controlling for confounding variables.

They also observed a dose-response relationship between smoking duration and colorectal polyps.

“Smoking duration of ≥ 20 years was positively associated with colorectal polyps, after adjustment for potential confounders, smoking intensity, and years since smoking cessation,” wrote Dr. Fliss-Isakov and coauthors. “In contrast, ≥ 20 years since smoking cessation was not associated with colorectal polyps, adjusting for smoking intensity and smoking duration.”

These findings are in line with only some previous research, contributing to mixed findings on the topic.

“These results, if confirmed by prospective studies, may indicate the need to incorporate smoking history and details of smoking habits into screening guidelines,” Dr. Fliss-Isakov and coauthors concluded.

With respect to all smoking parameters, the researchers observed stronger associations with serrated vs adenomatous polyps and distal vs proximal polyps.

The authors acknowledged that one potential limitation of this study was that its power was low with respect to serrated polyps because only a small sample size of patients had these lesions.