Carotenoids and cervical, breast, ovarian, and colorectal cancer.
Epidemiology and clinical trials*
Cheryl L. Rock
Department of Family and Preventive Medicine, University
of California, San Diego, La Jolla, CA 92093, USA
Abstract: Recent observational studies and clinical
trials that have investigated the relationship between carotenoids (or
diets rich in these compounds) and cervical, breast, ovarian, and colorectal
cancer have increased knowledge in this area. Although epidemiological
studies suggest a protective association, five randomized controlled
trials testing the effect of beta-carotene supplementation on regression
of cervical dysplasia, a preneoplastic lesion, did not find an effect
on rate of regression. In the Women's Healthy Eating and Living (WHEL)
Study, the effects of a high-vegetable carotenoid-rich diet on disease-free
survival following treatment for breast cancer is being examined in
a randomized multicenter diet intervention trial. Few epidemiological
studies of dietary factors and risk for ovarian cancer have been conducted,
with mixed results. Early case-control and cohort studies of colorectal
cancer have generally suggested a protective effect of vegetable consumption,
although a recent large cohort study did not confirm this relationship.
In two randomized trials, beta-carotene supplementation was not observed
to reduce risk of adenoma recurrence. The Polyp Prevention Trial (PPT),
which tested the effect of prescribing increased fruit, vegetable, and
fiber intake, and reduced dietary fat, revealed no effect of these efforts
on adenoma recurrence in the intent to treat analysis. However, serum
carotenoid concentrations were associated with decreased risk of recurrence
in that study. To move this area of study forward, more research on
mechanisms, surrogate biomarkers, and dietgene interactions is
*Lecture presented at the 13 th International Symposium
on Carotenoids, Honolulu, Hawaii, USA, 6-11 January 2002.
Other lectures are published in this issue, pp. 1369-1477.
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