Recruitment for the beta-carotene and retinol efficacy trial (CARET) to prevent lung cancer in smokers and asbestos-exposed workers

Our plain-English summary of Recruitment for the beta-carotene and retinol efficacy trial (CARET) to prevent lung cancer in smokers and asbestos-exposed workers, by G.S. Omenn, G. Goodman, J. Grizzle, et al (The Western Journal of Medicine, 1992).

The study

• Authors: G.S. Omenn, G. Goodman, J. Grizzle, M. Thornquist, L. Rosenstock, S. Barnhart, G. Anderson, J. Balmes, J. Cone, M. Cherniack
• Journal: The Western Journal of Medicine
• Published: 1992;156(5):540-4
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Free full text

Summary of the article

The authors described the design and recruitment strategy of the beta-Carotene and Retinol Efficacy Trial (CARET) and answered questions physicians might ask about patients taking part. CARET was a two-armed, double-blind, randomized trial testing whether beta-carotene (30 mg per day) plus retinol (25,000 IU per day) would reduce lung cancer incidence in heavy smokers and in asbestos-exposed workers who had smoked. The Vanguard group came from pilot studies run in Seattle from 1985 to 1988: 1,029 smokers and 816 asbestos-exposed participants, who accumulated 3,000 person-years of treatment. Recruitment of the Efficacy group began in 1989 at six centers: Seattle, Portland, San Francisco, Irvine, Baltimore and New Haven. Asbestos-exposed men aged 45 to 69 were recruited through physicians, workers' compensation programs, labor unions, plaintiffs' attorneys and a Navy asbestos surveillance program. Smokers aged 50 to 69 were recruited mainly from health insurers. The authors estimated that 4,300 asbestos-exposed workers and 13,600 smokers were needed for 80% power to detect a 33% reduction over an average 6.5 years of follow-up. As of March 31, 1992, 10,709 of a goal of 17,906 participants had been randomized. Adherence exceeded 90%, and no differences in symptoms, signs or liver function had been found between the treatment and placebo arms. Mesothelioma was being evaluated in the asbestos-exposed cohort. The authors expected CARET, together with two other major trials, to show by the end of the decade whether these agents can be recommended.

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 article described the design and recruitment of the Beta-Carotene and Retinol Efficacy Trial (CARET). CARET was a two-armed, double-blind, randomized trial testing whether beta-carotene (30 mg per day) plus retinol (vitamin A, 25,000 IU per day) would reduce lung cancer in heavy smokers and in asbestos-exposed workers who had smoked. The article gave no lung cancer results because the trial was still enrolling people. Participants from earlier Seattle pilot studies (1,029 smokers and 816 asbestos-exposed workers) continued in the trial and had built up 3,000 person-years of treatment. In the pilot studies, the only increased sign was mild yellowing of the skin in people taking beta-carotene. The authors reported no differences so far between the treatment and placebo groups in monitored symptoms, signs or liver tests. Adherence was more than 90% among active participants. As of March 31, 1992, 10,709 people had been randomized, against a goal of 17,906. The authors expected CARET and two other trials to show by the end of the decade whether these vitamins could be recommended.

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: Description of the design and recruitment strategy of a two-armed, double-blind, randomized chemoprevention trial (CARET) that was in progress. No efficacy results are reported.
• Who was studied: The Vanguard group came from Seattle pilot studies run from 1985 to 1988: 1,029 smokers and 816 asbestos-exposed participants. The Efficacy group was recruited from 1989 at six study centers (Irvine, San Francisco area, Portland, Seattle, Baltimore, New Haven). Combined recruitment goals were 4,277 asbestos-exposed workers and 13,629 smokers (17,906 total). Asbestos workers were men aged 45 to 69. Smokers were men and women aged 50 to 69.
• Exposure: The intervention was oral beta-carotene 30 mg per day plus retinol 25,000 IU per day, compared with placebo. Participants were heavy smokers or asbestos-exposed workers who had smoked. Asbestos workers needed extensive occupational exposure. No fiber types are named. Asbestos workers were recruited from physicians' practices, workers' compensation programs, labor unions, plaintiffs' attorneys and the Navy Medical Asbestos Surveillance Program in Bremerton, Washington.
• Main results:
  • In the pilot studies, the doses raised blood levels without increasing the prevalence of any relevant symptom or sign, except mild yellowing of the skin among those receiving beta-carotene.
  • The Vanguard participants had accumulated 3,000 person-years of treatment before recruitment of the Efficacy group began in 1989.
  • Adherence to the dose was more than 90% among active participants.
  • To date, the authors found no differences between the placebo and treatment arms for any monitored symptom or sign or for liver function tests.
  • The authors found no progressive increase in serum triglyceride levels.
  • The authors estimated that 4,300 asbestos-exposed workers and 13,600 smokers and former smokers were needed for 80% power, with an average follow-up of 6.5 years.
  • As of 3/31/92, 10,709 participants had been randomized across all study centers, against a total goal of 17,906.
• The authors' conclusion: The authors expected CARET, together with the results of two other major trials, to determine by the end of the decade whether vitamin A and beta-carotene can be recommended as chemopreventive agents against lung cancer, both to occupationally defined high-risk groups and to the public.
• Limitations the authors state:
  • The study's power will be diluted by placebo-arm participants taking these vitamins on their own, and by treatment-arm participants not taking their capsules.
  • Imperfect adherence, the time lag until full effect, and competing causes of death reduce the observable effect from 33% to a projected actual reduction of 22%.
  • Cancers other than lung cancer do not occur often enough to give useful statistical power.

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: Lung Cancer, Plaintiff, Mesothelioma.

Related studies

• 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)
• 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)
• 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)
• Changes in cholesterol and triglyceride concentrations in the Vanguard population of the Carotene and Retinol Efficacy Trial (CARET) — B. Cartmel, J. Dziura, et al. (2005)
• Lobe of origin and histologic type of lung cancer associated with asbestos exposure in the Carotene and Retinol Efficacy Trial (CARET) — C.A. Brodkin, J. McCullough, et al. (1997)
• Participation and adherence among older men and women recruited to the Beta-Carotene and Retinol Efficacy trial (CARET) — M.D. Thornquist, D.L. Patrick, et al. (1991)

Browse more research in The Western Journal of Medicine, or return to medical research.