Effects of supplemental alpha-tocopherol and beta-carotene on colorectal cancer: results from a controlled trial (Finland)
BACKGROUND
Some epidemiological investigations suggest that higher intake or biochemical status of vitamin E and beta-carotene might be associated with reduced risk of colorectal cancer.


METHODS
We tested the effects of alpha-tocopherol and beta-carotene supplementation on the incidence of colorectal cancer in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, a double-blind, placebo-controlled trial among 29,133 50-69-year-old male cigarette smokers. Participants were randomly assigned to receive alpha-tocopherol (50 mg), beta-carotene (20 mg), both agents, or a placebo daily for 5-8 years. Incident colorectal cancers (n = 135) were identified through the nationwide cancer registry, and 99% were histologically confirmed. Intervention effects were evaluated using survival analysis and proportional hazards models.


RESULTS
Colorectal cancer incidence was somewhat lower in the alpha-tocopherol arm compared to the no alpha-tocopherol arm, but this finding was not statistically significant (relative risk (RR) = 0.78, 95% confidence interval (CI) 0.55-1.09; log-rank test p = 0.15). Beta-carotene had no effect on colorectal cancer incidence (RR = 1.05, 95% CI 0.75-1.47; log-rank test p = 0.78). There was no interaction between the two substances.


CONCLUSIONS
Our study found no evidence of a beneficial or harmful effect for beta-carotene in colorectal cancer in older male smokers, but does provide suggestive evidence that vitamin E supplementation may have had a modest preventive effect. The latter finding is in accord with previous research linking higher vitamin E status to reduced colorectal cancer risk.
Albanes
D
D
Division of Clinical Sciences, National Cancer Institute, NIH, Bethesda, MD, 20892, USA.
Malila
N
N
Taylor
P R
PR
Huttunen
J K
JK
Virtamo
J
J
Edwards
B K
BK
Rautalahti
M
M
Hartman
A M
AM
Barrett
M J
MJ
Pietinen
P
P
Hartman
T J
TJ
Sipponen
P
P
Lewin
K
K
Teerenhovi
L
L
Hietanen
P
P
Tangrea
J A
JA
Virtanen
M
M
Heinonen
O P
OP
D000368:Aged; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000401:mortality / Q000517:prevention & control*; D019587:Dietary Supplements; D004311:Double-Blind Method; D005387:Finland / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking; D014810:Vitamin E / Q000008:administration & dosage*; D019207:beta Carotene / Q000008:administration & dosage*
D019207:beta Carotene; D014810:Vitamin E