PORTLAND, Ore. – Janet Penner had been taking estrogen and progestin for five years as a subject in the Women’s Health Initiative when in 2002 that study showed that long-term use of the hormones significantly increased a woman’s risk of breast cancer.

Penner immediately stopped taking the hormones, as did nearly all 8,500 study volunteers who had used them. Now, in a follow-up study appearing this week in the Journal of the American Medical Association, researchers have found that the elevated risk of breast cancer may persist for years after stopping hormone-replacement therapy.

Penner, a Portland resident in her 60s, has decided not to be alarmed by the news.

“If you are going to go into a medical study, one would expect that maybe there will be some surprises along the way,” she says. Despite the personal risks, Penner draws satisfaction from knowing that taking part helped produce valuable information for women’s health.

An actress and former theater costumer, Penner has raised three children and now helps keep the books for two family-owned businesses. She jumped at the chance to join the study in 1997 because she was outraged by a lack of research using women as subjects. Until the 1990s – when Congress passed a law requiring federally funded clinical trials to include more women – medical researchers and drug companies routinely carried out clinical trials of new treatments without including women.

“It was so unbelievably irritating to watch health study after health study being run for men,” Penner says. “It was good to see at least something focused exclusively on women.”

The Women’s Health Initiative, a clinical trial of disease prevention strategies, involved more women than any other prevention study in U.S. history.

Because the study was blinded, Penner wasn’t told whether she was getting hormone therapy or an inactive placebo. But when her severe hot flashes suddenly disappeared, she knew she was getting the hormones. She says a male-dominated medical industry hasn’t taken menopause symptoms seriously enough.

“Hot flashes sound like such a minor thing. You’re not going to die of it. It’s not cancer,” she says. But her symptoms robbed her of sleep, interfered with work and ruined attempts at relaxation.

Before the study, hormone-replacement therapy was widely prescribed, partly based on the belief it would protect women from cardiovascular disease. The Women’s Health Initiative showed the most common form of hormone therapy offered no protection from heart attack and actually increased the risk of stroke and breast cancer.

Penner says the information gleaned is worth the risk she took as a research volunteer.

“What do you do now? You just watch and wait and hope they keep finding answers,” she says.