Carotene and Retinol Efficacy Trial (CARET)

Lead Contacts and/or Principal Investigators (PIs):

Years Funded: 1985-2005
Funding Source: Fred Hutchinson Cancer Research Center and previously NCI Extramural Program (Division of Cancer Prevention)
Year(s) of Enrollment: 1985-1994
Study Website: Web Site Policy

The Carotene and Retinol Efficacy Trial (CARET) was a randomized, double-blind, placebo-controlled trial of the cancer prevention efficacy and safety of a daily combination of 30 milligrams (mg) of beta-carotene and 25,000 IU of retinyl palmitate in 18,314 persons who were at high risk for lung cancer. The investigators studied two high-risk populations: 4,060 men with extensive occupational exposure to asbestos, and 7,965 men and 6,289 women with at least 20 pack-years of cigarette smoking history. CARET began in 1985 with two pilot studies (Vanguard cohort) and expanded to six sites beginning in 1988 (Efficacy cohort). The study design projected active intervention until 1997, encompassing 110,000 person-years of follow-up for the 18,314 randomized participants.

The CARET intervention was halted in January 1996, 21 months ahead of schedule, with twin conclusions for definitive evidence of no benefit and substantial evidence of a harmful effect of the intervention on both lung cancer incidence and total mortality. During the intervention phase of CARET, serum, plasma, whole blood, and lung tissue specimens were collected. These biospecimens make up the CARET BiorepositoryExternal Web Site Policy.

The overall results of CARET were presented at a special NCI press conference January 18, 1996, followed by a publication (NEJM 334:1150-5, 1996). Further details about lung cancer were published soon afterward (JNCI 88:1550-9, 1996). Findings on lung cancer incidence and cardiovascular disease mortality during the first six years of post-intervention follow-up were published in 2004 (JNCI 96:1743-50, 2004).

On June 30, 2005, CARET stopped active follow-up of participants. However, CARET continues to support the extensive biological repository and ancillary studies that use the samples and data.

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