Study finds closer tie for smoking, colon cancer
SAN FRANCISCO, April 4 (Reuters) - Smoking cigarettes appears more closely tied to colon cancer than previously known, U.S. government researchers said Tuesday as they announced new findings about the causes of colorectal and stomach cancer.
Experts already had connected tobacco use to certain types of growths in the colon that can turn cancerous. Now, researchers from the National Cancer Institute said they believed smoking was a contributing factor to development of the more aggressive growths and colon cancer itself.
The preliminary findings by NCI scientists were based on answers to questionnaires about smoking habits from more than 1,900 people with precancerous polyps, known as adenomas, or colon cancer. The data showed higher rates of both among people who smoked cigarettes, said NCI epidemiologist Richard Hayes.
``We found associations for tobacco use for adenomas and for colon cancer,'' said Hayes, who spoke to reporters attending the annual meeting of the American Association for Cancer Research.
Colon cancer is the second most common cause of cancer deaths in the United States after lung cancer. More than 25,000 people die from colon cancer each year, Hayes said. Previous research has suggested that a high-fat, low-fiber diet may contribute to the disease.
The NCI study also showed that colon cancer risk was affected by how many years and how much people smoked. Quitting smoking appeared to lower the chances of colon cancer, Hayes said.
``The longer someone used cigarettes the greater the risk was, and also the amount of tobacco use,'' Hayes said.
The findings should give people one more reason to avoid smoking, said one researcher who reviewed the NCI figures.
The study ``implicates tobacco in yet another one of the big four diseases that strike people with cancer -- colon, lung, breast and prostate cancer,'' said Dr. Louis Weiner of the Fox Chase Cancer Center in Philadelphia.
In a separate study, NCI researchers said they were starting to better understand the role of a common bacteria in stomach cancers.
Helicobacter pylori, or H. pylori, bacteria paves the way for stomach cancer in patients with a certain genetic make-up that causes inflammation and allows inhibition of stomach acid, a natural defense against cancer, said Dr. Emad El-Omar, an NCI visiting scientist.
Previously, scientists had not been able to understand why half of the world's population carried the bacteria but not all developed cancer. Some get ulcers from H. pylori while other people show no harmful symptoms.
``Our findings provide a plausible explanation for the link between this infection and stomach cancer,'' El-Omar said.