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ß-Carotene Supplementation for Patients with Low Baseline Levels and Decreased Risks of Total and Prostate Carcinoma

Nancy R. Cook, Meir J. Stampfer, Jing Ma, et. al.
Abramson Cancer Center of the University of Pennsylvania
Last Modified: November 1, 2001

Reviewers: Li Liu, MD
Source: Cancer, 86(9): 1783-1792, November 1999.

Background

Some recent studies have suggested that several dietary antioxidants may reduce the risks of developing prostate cancer. The Physicians' Health Studyis a well-known, randomized, double blind placebo-controlled trial of ß-carotene (50 mg every other day) and aspirin, designed to evaluate a number of health outcomes. A previous analysis of data failed to demonstrate any protective effect of ß-carotene supplementation on total or prostate cancer incidence in the cohort. The current study looked at the potential benefits of ß-carotene supplements in the subgroup of participants who had lower than average plasma baseline levels of ß-carotene.

Methods

Baseline plasma ß-carotene levels were measured from nearly 15,000 male physicians prior to randomization. The team focused on the effects of ß-carotene on cancer risk in 1,439 men who subsequently developed cancer during 12 years of follow-up and 2,204 matched controls from the cohort.

Results

• There was a modest and nearly significant increase in risk of developing cancer for men in the lowest versus the highest quartile of baseline plasma ß-carotene level.
• Men in the lowest quartile of initial plasma ß-carotene who subsequently randomized to receive ß-carotene supplementation experienced a significant reduction in risk of prostate carcinoma.
• Men in the highest baseline quartile, ß-carotene supplements were associated with non-significant 33% increase in risk of prostate cancer.

Discussion

ß-carotene supplements appeared to reduce risk of developing prostate carcinoma among men with low baseline plasma ß-carotene levels. In contrast, men with higher concentrations of plasma ß-carotene may not benefit or may even show an increased risk of prostate carcinoma with ß-carotene supplementation. Additional investigation is needed to assess efficacy and optimal dosing of ß-carotene supplements for men with low baseline plasma ß-carotene level.