PI: Gary Goodman MD MS
Co-PI: Mark Thornquist PhD
CARET is a randomized, double-blind, placebo-controlled trial of the cancer prevention efficacy and safety of a daily combination of 30 mg of b-carotene and 25,000 IU of retinyl palmitate in persons at high risk for lung cancer. We 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 25 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 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 the twin conclusions of definitive evidence of no benefit and substantial evidence of a harmful effect of the intervention on both lung cancer incidence and total mortality. CARET overall results 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 (JNCI 88:1550-9, 1996) soon after.
To address the primary aim of the trial, we continue to follow CARET participants to determine time course for the active:placebo relative risks of cancer and death. We are investigating whether the relative risks changes after withdrawal of the study vitamins and, if so, how promptly the excess risks vanish or even reverse. We continue to follow the CARET participants through annual mailings.
The CARET specimen bank is a valuable resource for population based studies of the major human cancers. CARET is one of the few trials that has prospectively collected serum, plasma, whole blood, blood spots (for DNA), and lung cancer tumor specimens, as well as smoking history and serial food frequency questionnaires (in some individuals for up to 12 years) in these high-risk populations. This wealth of information in over 18,000 individuals makes the CARET specimen bank a special resource for cancer researchers. It is important that this resource be available to a wide range of researchers for hypothesis-driven studies.
Contact: Cim Edelstein
