Noncontraceptive estrogen use and the risk of breast cancer
D. W. Kaufman, D. R. Miller, L. Rosenberg, S. P. Helmrich, P. Stolley, D. Schottenfeld and S. Shapiro
The relation between the risk of breast cancer and the use of
noncontraceptive estrogens was investigated in a hospital-based study of
1,610 women with breast cancer and 1,606 with other conditions. The overall
relative risk estimate for conjugated estrogens first taken at least 18
months before admission, compared with never-use of any noncontraceptive
estrogens, was 0.9 (95% confidence interval, 0.7 to 1.1). For other
estrogens first taken at least 18 months before admission, the estimate was
0.8 (0.6 to 1.1). The results were similar when known risk factors for
breast cancer were taken into account. Among postmenopausal women,
conjugated estrogens did not appear to increase the risk of breast cancer,
even when taken for many years or in the distant past. There was no
evidence of an increased risk due to conjugated estrogen use among
subgroups of women defined according to various risk factors for breast
cancer. The results of this study suggest that noncontraceptive estrogens
do not increase the risk of breast cancer.
