'Natural' cancer prevention trial halted

Our plain-English summary of 'Natural' cancer prevention trial halted, by K. Peterson (Science, 1996).

The study

• Author: K. Peterson
• Journal: Science
• Published: 1996;271(5248):441
• Type of article: News
• Cited by: 18 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Summary of the article

This news report in Science described the National Cancer Institute's (NCI) announcement that two clinical trials it sponsored, in which volunteers took beta carotene to prevent cancer and heart disease, had yielded negative results. The report noted that two years earlier a Finnish study had suggested that beta carotene might raise the risk of lung cancer in smokers, a result many researchers had dismissed as a fluke. The Beta Carotene and Retinol Efficacy Trial (CARET), led by Gilbert S. Omenn of the University of Washington, Seattle, gave its 18,314 participants, who were smokers and people exposed to high levels of asbestos, daily doses of beta carotene, vitamin A, or a placebo for about 8 years. Those taking beta carotene had 28% more lung cancers and 17% more deaths than the group taking a placebo. Omenn stopped the $42 million trial on 10 January, 21 months early, and said the investigators did not know why these effects were observed. The second trial, the $22.5 million Physicians' Health Study, involved 22,071 doctors, 11% of them smokers, who took beta carotene or a placebo every other day for 12 years. The regimen did no harm, but it did not appear to help prevent cancer or cardiovascular disease. NCI Director Richard Klausner concluded that beta carotene is no magic bullet and that there is no substitute for stopping smoking.

PubMed has no abstract for this study, and the article doesn't print one. We wrote this summary from the full article with the help of AI. It is not the authors' wording.

In plain English

This is a short news report in Science, not a research paper. The author described results announced by the U.S. National Cancer Institute from two clinical trials of beta carotene supplements. In the Beta Carotene and Retinol Efficacy Trial (CARET), 18,314 participants, who were smokers and people exposed to high levels of asbestos, took daily beta carotene, vitamin A, or a placebo for about 8 years. The report said those taking beta carotene had 28% more lung cancers and 17% more deaths than the placebo group. The trial was stopped 21 months early because of concern about a possible cancer risk. The report gave no separate figures for the asbestos-exposed participants, no confidence intervals, and no details of their asbestos exposure. In the second trial, the Physicians' Health Study, 22,071 doctors (11% of them smokers) took beta carotene or a placebo every other day for 12 years. The regimen did not appear to cause harm, nor to help prevent cancer or cardiovascular disease. CARET's lead investigator, Gilbert Omenn, was quoted as saying the team did not know why these effects were observed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: news report describing the announced results of two clinical trials sponsored by the National Cancer Institute (not an original research article)
• Who was studied: CARET: 18,314 participants who were smokers and people exposed to high levels of asbestos. The Physicians' Health Study (22,071 doctors) is described under results.
• Exposure: CARET participants took daily beta carotene, vitamin A, or a placebo for about 8 years. Asbestos exposure was a characteristic of part of the trial population. No fiber types, jobs or doses are given.
• Main results:
  • In CARET, those taking beta carotene had 28% more lung cancers and 17% more deaths than the group taking a placebo. No separate figures are given for asbestos-exposed participants.
  • CARET was stopped 21 months early because of concern about a possible cancer risk.
  • The second trial, the Physicians' Health Study, involved 22,071 doctors, 11% of them smokers.
  • In the Physicians' Health Study, in which participants took beta carotene or a placebo every other day for 12 years, the regimen did not do harm but did not seem to help prevent cancer or cardiovascular disease.
• The authors' conclusion: The news report draws no conclusion of its own. CARET's lead investigator, Gilbert Omenn, was quoted as saying the researchers did not know why these effects were observed.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer.

Medical terms in this study, explained in our Lexicon: Clinical Trial, Lung Cancer.

Related studies

• Research cost analyses to aid in decision making in the conduct of a large prevention trial, CARET. Carotene and Retinol Efficacy Trial — M.D. Thornquist, N. Urban, et al. (1993)
• CARET, the beta-carotene and retinol efficacy trial to prevent lung cancer in asbestos-exposed workers and in smokers — G.S. Omenn, G. Goodman, et al. (1991)
• Vitamin A and cancer prevention II: comparison of the effects of retinol and beta-carotene — N.H. de Klerk, A.W. Musk, et al. (1998)
• Modulation of genotoxic and related effects by carotenoids and vitamin A in experimental models: mechanistic issues — S. De Flora, M. Bagnasco, et al. (1999)
• Risk factors for lung cancer and for intervention effects in CARET, the Beta-Carotene and Retinol Efficacy Trial — G.S. Omenn, G.E. Goodman, et al. (1996)
• Recruitment for the beta-carotene and retinol efficacy trial (CARET) to prevent lung cancer in smokers and asbestos-exposed workers — G.S. Omenn, G. Goodman, et al. (1992)

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