Objectives: Plasma DHEA and its sulfate (DHEA-S) are positively associated with breast cancer risk in postmenopausal women; but the relationships have not been studied in detail in premenopausal women. We prospectively evaluated relationships between plasma levels of DHEA and DHEA-S in blood samples provided by a group of primarily premenopausal women and subsequent breast cancer, by use of case-control sampling from the Nurses' Health Study cohort.
Method: Blood samples were collected from 1989 to 1990. Among women who were not postmenopausal at blood collection, 302 were diagnosed with breast cancer between blood collection and June 1998. Two controls were selected per case and matched with respect to age, menopausal status, month and time of day of blood collection, and fasting status at blood collection. Statistical analyses using conditional logistic regression were done to adjust for potential confounders.
Results: At time of blood collection, the median age was 49 (10th to 90th percentiles 45 to 53). In multivariable analyses, the highest quartile of DHEA was associated with an odds ratio of breast cancer of 0.92 (95% confidence interval, 0.59-1.43) relative to the lowest quartile (P value for log-linear trend 0.11). A similar analysis revealed an odds ratio of 1.08 (0.69-1.69) for DHEA-S (P value for log-linear trend 0.83). No statistically significant interactions were noted according to certainty of menopausal status, age, or past oral contraceptive use.
Discussion: Our analysis did not reveal a relationship between DHEA or DHEA-S and subsequent breast cancer in middle-aged premenopausal women. In the future, this relationship should be studied in younger women.