Wednesday, March 23, 2005

Chemoprevention Strike Two

Recently there’s been some attention paid to the CARET study, a chemoprevention study in which heavy smokers [really heavy smokers] and asbestos exposed workers were provided Vitamin A to test whether anti-oxidants retard development of lung cancers. Instead, it was found that the treatment accelerated the development of lung cancers. The study was stopped.

Diet and cancer studies suggest various “healthy” practices, including anti oxidant intake protect against cancer. By discrediting the biological basis for Vitamin A protection, the CARET study suggests that maybe all the “healthy living protects” results are uncontrolled confounding.

The study reported here added Vitamin E. About 30,000 male Finnish smokers were followed for up to 8 years. No reduction in incidence was observed among the men who received vitamin E. A higher incidence of lung cancer among the men who received Vitamin A than among those who did not. Fewer cases of prostate cancer were diagnosed among those who received alpha-tocopherol than among those who did not. Beta carotene had little or no effect on the incidence of cancer other than lung cancer. Alpha-tocopherol had no apparent effect on total mortality. Total mortality was 8 percent higher (95 percent confidence interval, 1 to 16 percent) among the participants who received beta carotene than among those who did not, primarily because there were more deaths from lung cancer and ischemic heart disease.


The Effect of Vitamin E and Beta Carotene on the Incidence of Lung Cancer and Other Cancers in Male Smokers

Beta Carotene Cancer Prevention Study Group The Alpha-Tocopherol

NEJM Volume 330:1029-1035 April 14, 1994

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