The use of hormone therapy was associated with a reduced risk of breast cancer in postmenopausal women who carry BRCA mutations, according to a case-control study published online September 23 in the Journal of the National Cancer Institute.
Women who carry a mutation in the BRCA1 gene may opt to have their ovaries removed to lower their risk of developing breast cancer. The surgery, however, induces menopause, and thus some women opt to take hormone therapy to reduce its symptoms. The impact of hormone therapy on the risk of breast cancer in these women is not known.
To find out, Steven Narod, M.D., of the University of Toronto and colleagues compared the use of hormone therapy in 236 breast cancer patients and 236 matched control subjects. All of the study participants carried a mutation in BRCA1.
Narod and colleagues report that 68 (29%) of the control subjects had used hormone therapy at some time, as had 47 (20%) of the women in the breast cancer group. The use of hormone therapy was associated with a 42% relative reduction in the risk of developing breast cancer. The researchers did not find a difference in risk reduction associated with estrogen-only or estrogen-progesterone therapies, however the reduction did not reach statistical significance in the estrogen-progesterone subgroup. The researchers did not detect a difference in risk reduction between women who had undergone natural, age-related menopause and those who had undergone surgically induced menopause.
"The magnitude of the association appeared to be as great, or even greater, for women after surgical menopause than it was for women after natural menopause. This information should be reassuring to women who wish to undergo preventive oophorectomy before menopause, but it needs to be confirmed in subsequent studies," the authors write.
In an accompanying editorial, Rowan Chlebowski, M.D., Ph.D., of the Los Angeles Biomedical Research Institute at Harbor-University of California Los Angeles Medical Center, and Ross Prentice, Ph.D., of the Fred Hutchinson Cancer Research Center in Seattle caution that observational studies have misled the field previously. Whereas earlier observational trials suggested that hormone therapy was not associated with an increased risk of breast cancer recurrence, randomized trials found a statistically significant increase in risk with menopausal hormone therapy use in breast cancer survivors.
"The results presented by [Narod and colleagues] regarding hormone therapy use in postmenopausal BRCA1 mutation carriers provide some evidence for safety but are insufficient to reliably inform routine clinical practice," the editorialists write. "As a result, continued caution in prescribing hormone therapy to women with BRCA1 mutations who are at high risk for breast cancers remains prudent."