In another piece of the increasingly complex hormone-replacement health puzzle, women given estrogen-only therapy after menopause ran a significantly higher risk of ovarian cancer, researchers reported Tuesday.
The report followed two other recently released studies that found estrogen in combination with progestin — a slightly less common replacement therapy than estrogen-only — does not generally protect against heart disease after all and may increase the risk of breast cancer, stroke and blood clots.
Hormone replacement therapy (HRT) of both types is used by an estimated 13.5 million women in the United States alone, nearly 8 million estrogen-only and up to 6 million in combination with progestin.
The therapy is prescribed to treat immediate symptoms such as hot flashes and vaginal dryness, and to protect against bone-thinning osteoporosis.
James Lacey of the National Cancer Institute, lead author of the estrogen study published in this week’s Journal of the American Medical Association, said there was not enough evidence to say if there was also an ovarian cancer risk from estrogen-progestin use.
He offered this advice to women: “Because hormone therapy may influence so many conditions ... after menopause — cardiovascular disease, osteoporosis, breast cancer, uterine cancer, gallbladder disease, blood clots, and now potentially ovarian cancer — we should no longer think of a woman basing her decision to use hormones on the potential risk of just one condition.
“Women should continue to talk to their health care providers about whether hormones might be right for them.”
Lacey’s research involved 44,241 post-menopausal women whose health histories were tracked for about 20 years as part of a major breast cancer study. Among those women, 329 developed ovarian cancer. The researchers found that compared to similar women not on hormones, those taking estrogen therapy had a 60 percent greater risk of developing ovarian cancer.
The risk increased proportionately with longer duration of hormone use; those who used estrogen therapy for 20 or more years were approximately three times more likely to develop ovarian cancer. However, women who used an estrogen-progestin combination did not appear to have a significantly increased risk of ovarian cancer.
“The main finding of our study was that post-menopausal women who used estrogen replacement therapy for 10 or more years were at significantly higher risk of developing ovarian cancer than women who never used hormone replacement therapy,” Lacey said in a statement released by the cancer institute.
The institute said that as early as the 1940s women began using estrogens in high doses to counteract some of the short-term discomforts of menopause; but after it became clear in the 1970s that it carried a high risk of uterine cancer, doctors began prescribing progestin, along with much lower doses of estrogen.
But it’s been thought that for women who have had hysterectomies and who need HRT, estrogen alone may be safer.
The women in the NCI study varied — some had undergone hysterectomy, but all had at least one ovary.
The study authors noted that earlier studies on the connection between hormone therapy and ovarian cancer were unclear. A major study released last year found a two-fold increased risk of ovarian cancer among hormone users, but did not distinguish between those on estrogen and combined regimens.
In an accompanying editorial, Dr. Kenneth Noller of Tufts University and New England Medical Center in Boston said that while the latest research doesn’t establish a causal connection between estrogen therapy and ovarian cancer, the association should be worrisome enough for doctors to weigh carefully whether to suggest estrogen-only therapy.
He noted that it’s still common for women who have had a hysterectomy but who retain one or both ovaries to be prescribed estrogen-only therapy.
“Estrogen replacement therapy certainly is not the panacea it once appeared. Physicians counseling women about HRT must consider the unique needs of each patients and attempt to weigh the benefits and risks on an individual basis,” he said.
While the estrogen-progestin arm of the Women’s Health Initiative was halted last week after researchers found the overall risks outweighed the benefits, the estrogen-only arm was allowed to continue. The results of that trial are expected to answer remaining questions about estrogen therapy once and for all.
Reuters contributed to this story.