Vitamin C, beta-carotene, and an anti-bacterial treatment may -- singly or in combination -- help prevent stomach cancer, according to a long-term clinical trial involving more than 600 people at high risk of developing the disease. The results of the trial appear in the Dec. 6, 2000, issue of the Journal of the National Cancer Institute.
Gastric cancer is the second leading cause of cancer death in the world and five-year survival rates are low. An effective means of preventing the disease could have a dramatic impact on public health worldwide.
Pelayo Correa, M.D., and colleagues at Louisiana State University, New Orleans, together with researchers from Colombia, conducted the trial in an area of Colombia known for its high rate of stomach (gastric) cancer. Participants were randomly assigned to receive either:
- a standard treatment for H. pylori infection, a bacteria that has been associated with the development of gastric cancer;
- one gram of ascorbic acid (vitamin C) twice a day;
- 30 milligrams of beta-carotene once a day;
- various combinations of these treatments; or
- a placebo.
To compare the treatments, the researchers looked at the status of precancerous abnormalities in the stomachs of each of the participants over the course of the six-year study. They analyzed biopsy specimens at the beginning of the study, after three years, and again after six years. The biopsies showed that precancerous abnormalities were more likely to shrink or disappear among people who received treatment than among those who took placebos.
The three different treatments all had about the same effect, and combining treatments did not appear to add any advantage.
For example, among people with a precancerous abnormality known as nonmetaplastic atrophy, those who received the anti-H. pylori treatment (an antibiotic plus other agents) were 4.8 times more likely than the placebo group to undergo a regression in their abnormalities. People with this condition receiving vitamin C were 5.0 times more likely to have abnormalities that regressed, and those receiving beta-carotene, 5.1 times more likely.
In an accompanying editorial, William Blot, Ph.D., of the International Epidemiology Institute in Rockville, Md., notes that the findings agree with those of other studies showing that people who eat many fruits and vegetables, which are rich sources of ascorbic acid and beta-carotene, have lower rates of gastric cancer. He cautions, however, that the findings must be confirmed by other studies.
A number of gastric cancer prevention trials are under way around the world. The largest, Correa said, is taking place in the Shandong province of China, where gastric cancer rates are very high. Sponsored by the National Cancer Institute, this trial is comparing the effects of vitamin and mineral supplements, a garlic extract, and anti-H. pylori treatment. Other trials are under way in Italy, England, Mexico, and elsewhere.