The CancerWeb Report, What's New In Cancer: May, 1996
Cancer Prevention

• Beta Carotene - A number of epidemiological studies indicating a beneficial effect on cancer and on heart disease of vegetables and fruits rich in vitamin A have been interpreted as indicating that beta-carotene is protective against cancer development. Some laboratory studies have supported this idea. However, two major studies reported in the New England Journal of Medicine issue of May 2, describe disappointing results of long-term trials with beta-carotene as a cancer preventive. Interestingly, a third article in the same issue, ascribes cardiovascular benefit to vitamin E rather than to A.

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• A group from Harvard and Oxford Universities describe the study began in 1982 involving 11,036 physicians randomly assigned to receive beta carotene (50 mg on alternate days) and 11035 receiving placebo. By the end of 1995, there were no overall differences in the incidence of malignant disease (1273 had malignant disease with beta carotene and 1293 without; cancer deaths, 386 versus 380; or lung cancer cases, 82 versus 88), cardiovascular disease, stroke (367 versus 382), or overall mortality. (Henneeken, NEJ Med 334:1145, 1996)

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• In a second multicenter randomized study, 18,314 smokers, former smokers, and workers exposed to asbestos, all groups with a higher risk of lung cancer, were given 30 mg of beta carotene and 25,000 IU of vitamin A as retinyl palmitate daily. There were 388 new cases lung cancer in all during an average of four years observation, but the treated group had an elevated relative risk of 1.28 compared with the placebo group, and there were no differences for other cancers. The relative risk of death from cardiovascular causes was also up, at 1.26. The trial was stopped 21 months early because of these findings, but follow-up is to continue for five more years. (Omenn NEJ Med 334:1150, 1996)