National Cancer Institute
Back to previous page

Carotene and Retinol Efficacy Trial (CARET)

Cohort Collaboration Contact

If interested in collaborating with the cohort on a project, please contact:

Principal Investigators

  • Gary Goodman (Fred Hutchinson Cancer Research Center)
  • Mark Thornquist (Fred Hutchinson Cancer Research Center)
  • Marian Neuhouser (Fred Hutchinson Cancer Research Center)
Cohort Website


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. The trial began recruitment in 1985 and was halted in January 1996, 21 months ahead of schedule, with the twin conclusions of no benefit and substantial evidence of a harmful effect of the intervention on both lung cancer incidence and total mortality. Participants were followed for over nine years post-intervention, with updated lung cancer incidence and cardiovascular disease mortality findings published in 2004. On June 30, 2005, CARET stopped active follow-up of participants. Passive follow-up to extend cancer and death outcomes through 2013 was conducted via linkages with select state cancer registries and the National Death Index (NDI). During the active intervention phase of CARET, serum, plasma, whole blood, and lung tissue specimens were collected. These biospecimens make up the CARET Biorepository.