Colon cancer may start earlier in men, current smokers, and current drinkers, a new study shows.
The finding could mean that those people should be checked for colon cancer at an earlier age, the researchers write. Currently, people at normal risk of colorectal cancer are due to begin routine colorectal screening at age 50.
Colorectal cancer is America’s No. 2 cause of cancer deaths, and early detection can boost survival, write Anna Zisman, MD, and colleagues in the Archives of Internal Medicine.
Zisman’s study raises many questions. Until those questions are answered, “the conclusions from our report should be limited to stating that drinking and smoking are markers for young age at colorectal cancer presentation,” the researchers write.
Zisman works in the internal medicine department at Northwestern University’s Feinberg School of Medicine in Chicago.
Studying Smoking, Drinking
“Smoking is a well-established colorectal cancer risk factor, associated with a twofold increase in risk and implicated in 12 percent of all colorectal cancer deaths,” Zisman and colleagues write.
“Results of most studies indicate that alcohol use causes a similar increase in colorectal cancer risk,” they continue. Cancer is complicated and many other factors — including genetics, lifestyle, and obesity — are also important, the researchers note.
Zisman’s team couldn’t track all of those factors at once. They focused on smoking and alcohol, studying more than 161,000 colorectal cancer patients from a large, national database.
Data showed alcohol or tobacco within the past year (current smokers or drinkers) or years earlier (past smokers or drinkers). Patients’ amount of tobacco or alcohol use, changes in those habits, and other lifestyle factors weren’t available.
Men were almost two years younger than women when diagnosed, the study shows.
Here are the results for current smokers and drinkers, compared with those who never smoked or drank:
Current smokers were diagnosed 5.2 years earlier. Current drinkers were diagnosed 5.2 years earlier. People who currently smoked and drank were diagnosed 7.8 years earlier.
Past alcohol or tobacco use had “minimal” effects, the researchers write, suggesting that “stopping drinking and smoking may mitigate the risk.” Current use was defined as using tobacco or alcohol within the past year.
The researchers adjusted for patients’ race and health insurance. But they couldn’t check the influence of diet, exercise, family history, socioeconomic status, and education level.
The study doesn’t include a cancer-free comparison group, and it doesn’t prove that smoking or drinking caused any of the patients’ colorectal cancers.
Sex, drinking, and smoking were also linked to the tumors’ locations.
Distal colorectal cancers — located on the lower left part of the colon and rectum — were more common in men, current smokers, and current drinkers. Proximal tumors — found on the right side of the colon — were more likely seen in nonsmoking, nondrinking women.
Those findings may mean that nonsmoking, nondrinking women should choose colonoscopy over flexible sigmoidoscopy, the researchers write.
In both tests, a thin, flexible tube is inserted through the rectum to check for colorectal cancers or polyps that might develop into cancer. Colonoscopy is a longer instrument, which can check the whole colon; flexible sigmoidoscopy doesn’t go as far.
Doctors may one day be able to tailor colorectal cancer screening to each patient’s unique traits, write the researchers. Meanwhile, they stress the importance of early detection, regardless of drinking and smoking.
By Miranda Hitti, Reviewed by Louise Chang, MD
SOURCES: Zisman, A. Archives of Internal Medicine, March 27, 2006; vol 166: pp 629-634. News release, JAMA/Archives.