Environment and Breast Cancer: Science Review

Evidence From Humans
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Plasma retinol, beta-carotene and vitamin E levels in relation to the future risk of breast cancer
Wald, N. J., Boreham, J., Hayward, J. L., Bulbrook, R. D. Br J Cancer. 1984. 49:3, 321-4.
Study design
Nested case-control
Funding agency
Not reported
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Post menopausal
Pre menopausal
Number in Cohort
Controls: 78; cohort 5,004
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
In: Women between the ages of 28 and 75 in the ICRF prospective study
Comment about participation selection
Women living on a small island: same basic characteristics and lack of diversity in food choice
Exposure Investigated
Exposures investigated
Beta carotene and vitamin E in plasma
Exposure assessment comment
Only one blood sample, lack of accuracy of plasma level of vitamins, length of time of plasma storage between 7 and 14 years
Statistical Analysis
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Not considered: BMI, alcohol consumption
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
OR, highest versus lowest quintile of serum level; p- value; follow-up 7-14 years; standardized mean stratified by menopausal status
Strength of associations reported
Beta carotene: OR=0.54, p- value= NS; vitamin E: OR =0.5, p -value<0.01
Results Comments
Plasma vitamin E level showed a clear association (low levels being associated with a significantly higher risk of cancer). Beta-carotene levels showed a similar tendency, but the effect was less strong, less consistent, and not significant.
Reviewers Comments
In a later publication (1988), the author raised concern that results may have been due to differences in handling cases and serum samples.