Women who take combination hormones for their menopausal symptoms become more likely to get an uncommon type of breast cancer much earlier than experts generally have believed, according to Seattle researchers.

Millions of women have already abandoned combination-hormone therapy because of well-publicized links to health problems, including breast cancer. But the new findings, released by the Fred Hutchinson Cancer Research Center, are the most detailed yet of a link to one specific cancer called lobular breast cancer, which is uncommon but particularly elusive because it doesn't form telltale lumps.

Because not everyone has dropped the combination therapy, the researchers say the study adds yet another factor for women and their doctors as they consider it to treat the worst hot flashes, night sweats and other miseries of menopause. Still, it may not matter to women who already are being careful to take hormones in low doses for short periods of time.

Based on previous studies, most researchers have assumed that it takes five years of combined-hormone therapy before the overall risk of developing breast cancer is elevated significantly.

But the new study found that women who took estrogen and progestin every day for as little as three years were about three times more likely to develop either lobular breast cancer or lobular-ductal breast cancer than those who had never taken hormones.

The study compared the histories of 1,044 postmenopausal breast-cancer patients from the Puget Sound, Wash., area with 469 women in a control group who did not have cancer.

The paper was published in the January issue of Cancer Epidemiology, Biomarkers and Prevention.

Lobular breast cancer, which accounts for an estimated 15 percent of the 178,000 invasive breast cancers diagnosed in the United States each year, forms in the milk-producing glands and grows in sheets that can be difficult to detect through physical breast exams and mammograms. Its numbers have risen sharply since the late 1980s in tandem with the growth in combined-hormone therapy.

Ductal breast cancer, the most common type of breast cancer, forms in the milk ducts and creates more familiar masses in the breasts.

The latest study revealed a specific connection between current estrogen/progestin therapy and lobular breast cancer, said Christopher Li, the study's first author. Women who had never taken hormones or who had stopping taking them -- or those who were taking estrogen only -- were not at higher risk of any types of breast cancer.

Nor did estrogen/progestin therapy raise the risk of ductal breast cancer.

Combination-hormone therapy has been declining at least since 2002, when a large federal study implicated it in a host of health problems. In August, another national study of 200,000 patients found that breast-cancer rates have fallen significantly since then.

But several million American women are on some kind of hormone therapy.

Dr. Nancy Tipton, a gynecologist with Virginia Mason Medical Center, said this week's study shouldn't change anything for patients who follow advice to take the lowest possible doses of hormones for the shortest possible time.

"Nothing is risk-free. A lot of women really need combination hormones for a while because they're miserable," said Tipton, who estimated that a quarter of her menopausal patients need estrogen-progestin to control their symptoms. "If it's [optimally] three years instead of five, OK, we'll deal with that."

Tipton, 55, said women should review every 12 to 18 months whether they're ready to forgo hormone therapy.

"I took myself off after a couple of years, and I was just fine," Tipton said.

Contact Kyung Song at 206-464-2423 or ksong@seattletimes.com.

Source: Seattle Times. Distributed by McClatchy-Tribune Information Services. Powered by Yellowbrix.

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