The CARET asbestos-exposed cohort: baseline characteristics and comparison to other asbestos-exposed cohorts.
The Carotene and Retinol Efficacy Trial (CARET) was a double-blind, placebo-controlled trial of the daily administration of 25,000 IU vitamin A and 30 mg beta-carotene for the prevention of lung cancer. Of close to 18,500 participants, more than 4,000 were asbestos-exposed men recruited from shipyard and construction trades at five study centers in the United States. While the primary endpoint of the trial was the incidence of lung cancer, a number of questions about the natural history of asbestos-related disease will also be addressed. The mean age at entry into the trial was 57 years and the mean duration of follow-up on active intervention was 4 years. With the exception of 133 never-smoker pilot participants (3%), all subjects recruited were by intention current (38%) or ex-smokers (58%), with a mean cumulative smoking exposure at entry of 43 pack-years. Mean years from first asbestos exposure were 35, and mean duration of asbestos exposure in a high-risk trade was 19 years. The distribution of radiographic abnormalities was as follows: normal, 34%; parenchymal opacities (ILO profusion score > 1/0) alone, 18%; pleural thickening alone, 27%; both parenchymal opacities and pleural thickening, 21%. The CARET cohort, when compared to previously reported asbestos-exposed cohorts, is characterized by substantial asbestos exposure and high proportion of asbestos-related radiographic findings. The active intervention was halted in 1996, after a mean duration of 40 years. Passive follow-up of the cohort will continue until the year 2000.
Barnhart
S
S
School of Public Health and Community Medicine, University of Washington, Seattle, USA. sbht@u.washington.edu
Keogh
J
J
Cullen
M R
MR
Brodkin
C
C
Liu
D
D
Goodman
G
G
Valanis
B
B
Glass
A
A
Thornquist
M
M
Rosenstock
L
L
Omenn
G
G
Balmes
J
J
D001194:Asbestos / Q000009:adverse effects*; D004311:Double-Blind Method; D006801:Humans; D008137:Longitudinal Studies; D008175:Lung Neoplasms / Q000209:etiology* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D009784:Occupational Diseases / Q000209:etiology* / Q000503:physiopathology; D016273:Occupational Exposure; D016032:Randomized Controlled Trials as Topic; D012129:Respiratory Function Tests; D012907:Smoking; D013147:Spirometry
D001194:Asbestos