Hormone therapy is commonly used to help treat women with menopause. However, this therapy can increase their risk of having abnormal mammograms and breast biopsies and may decrease the effectiveness of both methods for detecting breast cancer.
According to the study done by Rowan T. Chlebowski, M.D., Ph.D., of the Los Angeles Biomedical Research Institute at Harbor–UCLA Medical Center, and colleagues, the use of combined hormones increases breast density, which increases the risk of breast cancer and may also delay diagnosis.
The group studied 16,608 post-menopausal women who participated in the Women’s Health Initiative (WHI) clinical trial, beginning in 1993 through 1998. During the 5.6 years of the study, 199 women in the combined hormone group and 150 women in the placebo group developed breast cancer. Mammograms with abnormal results were more common among women taking hormones than among women taking placebo (35 percent vs. 23 percent); women taking hormones had a 4 percent greater risk of having a mammogram with abnormalities after one year and an 11 percent greater risk after five years.
Breast biopsies also were more common among women taking hormones than among those assigned to placebo (10 percent vs. 6.1 percent). “Although breast cancers were significantly increased and were diagnosed at higher stages in the combined hormone group, biopsies in that group less frequently diagnosed cancer (14.8 percent vs. 19.6 percent),” the authors said.
After discontinuation of combined hormone therapy, its adverse effect on mammograms modulated but remained significantly different from that of placebo for at least 12 months.

Source: JAMA