What's best for breasts?

Research suggests a connection between breast cancer and hormone-replacement therapy. Time to blame the estrogen?

Published December 15, 2006 11:10PM (EST)

Good news from the pink-hued annals of breast cancer research! A team at Houston's M.D. Anderson Cancer Center say breast cancer rates in the U.S. declined by 7 percent in 2003, the New York Times reports. That's a dramatic drop compared with the previous year's modest 1 percent decline, and an apparent reversal of a longtime trend in breast cancer rates, which have gradually risen since 1945. The biggest drop was in the number of women with estrogen-receptor-positive tumors, which account for 70 percent of breast cancer cases, and which declined by 15 percent from August 2002 to December 2003. Because 2002 was also the year that large numbers of women stopped hormone-replacement therapy (HRT), after a large clinical trial by the Women's Health Initiative found that women who took the Wyeth drug Prempro had slightly higher breast cancer rates, researchers hypothesize that the recent fall in breast cancer incidence can be explained by the falling popularity of HRT. The theory is that without HRT, many hormone-initiated tumors regressed, stopped growing or didn't develop in the first place. If the researchers are correct, decreasing breast cancer rates could be here to stay.

The finding doesn't come as a total surprise: Physicians and researchers already knew hormone-replacement therapy could feed estrogen-receptor-positive tumors, and research like the WHI study had shown a potential connection between hormones and cancer rates. Still, competing theories on environmental causes, lifestyle factors and demographics have long struggled to make sense of the increase in breast cancer rates, as well as the especially high rates in areas like Marin County and Long Island, so it would be a relief to have a conclusive answer.

As of now, though, the findings shouldn't be regarded as conclusive, since a possible connection between breast cancer rates and HRT does not amount to a public health advisory. I talked to Elena Elkin, a breast cancer researcher at Memorial Sloan-Kettering Cancer Center, who helped make sense of the big news.

"The hypothesis that declining breast cancer rates are related to a decline in hormone-replacement therapy is a plausible one, but because this is an ecological study, it doesn't provide evidence of a causal relationship," she said. (M.D. Anderson coauthor Peter Ravdin has also emphasized that "epidemiology can never prove causality.") "These results suggest a hypothesis that lower rates of hormone-replacement therapy have contributed to lower breast cancer incidence, but they don't confirm this hypothesis."

She said it's too soon to rule out other potential explanations for the drop in breast cancer rates because, at the moment, there are too many unknowns: "Of the women who were analyzed in this study, we don't know which individuals were on hormone-replacement therapy," she explained. "We also don't know whether the decline in incidence could be due to a change in rates of screening mammography, because we don't know which cancers were screen-detected and which were diagnosed in women who felt a breast lump. We also don't know whether the dramatic decline in breast cancer incidence will persist or whether it was a one-time reduction. So these findings are exciting and provocative, but they should prompt further research. Decisions about hormone replacement for any individual woman still need to be made in consultation with her physician, carefully considering all possible risks and benefits."

She added, "It is worth noting that the researchers did see a decrease in the incidence of estrogen-receptor-negative tumors, though it was a smaller decrease. And they saw a decline in all age groups; the decline was greatest for women in their 50s and 60s. And if fewer women are getting breast cancer, that's great news."

And really, the fact that it's great news is the take-away message here. But individual women making hormone-replacement decisions this week may be having a tough time. HRT is a complex subject, not only because more research is needed but also because hormone replacement speaks to loaded issues like femininity and aging as well as the pursuit of good health. The Times notes that in the '60s, physician Robert Wilson traveled the country promoting his squishily titled book "Feminine Forever," which likened women replacing lost estrogen to diabetics replacing lost insulin, and promised that HRT would keep aging women "young, healthy and attractive." Soon, pharma companies (like Wyeth) came out with hormone-replacement drugs (like Wyeth's Prempro) and raked in the dough. The Times reports that by 2002, around a third of American women over 50 were on hormones, and the fountain-of-youth idea hadn't really gone away: "Some women and doctors also believed, without any good evidence, that the pills could keep skin youthful, preserve memory and make women energetic," writer Gina Kolata notes. In age when postmenopausal women often report feeling invisible and menopause is often framed as a disease rather than a phase of life, it's easy to see why such a product would appeal.

Of course, many doctors and patients were and are interested in HRT for more tangible reasons: Taking hormones can help mitigate the frequently hellish effects of menopause, as well as help protect against heart disease and bone loss. So hormone replacement isn't just a hedge against aging in some abstract sense; many women turn to hormones to slow and manage the effects of aging in a practical sense. And for women seeking relief from hot flashes, insomnia and other menopause-related woes, the current hormone-heavy headlines may be hard to parse. For women who have been on hormones and had breast cancer, and the friends and families of those women, it's likely quite frustrating not to know whether hormones contribute to breast cancer, and hard not to wish they hadn't avoided HRT just in case.

Even promising findings on such a sensitive subject are likely to provoke controversy, so we'll continue to sift through expert opinions as they emerge. Keep an eye out for more coverage of the HRT-breast cancer connection in the coming week.

By Page Rockwell

Page Rockwell is Salon's editorial project manager.

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