Breast-cancer rates among Northwest women have plummeted since 2002, when thousands abruptly quit taking hormone-replacement medicines, a large new study shows.

The analysis, conducted at Kaiser Permanente’s Center for Health Research in Portland, confirms what another major study released this spring suggested: Breast-cancer rates and hormone use have traveled in tandem. Rates rose during the years when hormone therapy was commonly prescribed to alleviate menopause symptoms; they fell swiftly after 2002, when news that hormones held more risks than benefits prompted many women to dump the drugs.

As did a study published this spring in the New England Journal of Medicine, the new findings from Oregon suggest that hormone use played a key role in the disease rate’s rise and fall, said Dr. Andrew Glass, the study’s lead author. The new evidence, he said, should help women make decisions when it comes to alleviating or coping with hot flashes, sleeplessness and other sometimes debilitating symptoms of menopause.

“You can’t do anything about your genetic background or your family history,” Glass said in an interview last week. “But you can do something about the medicine you put in your mouth.”

The study was published today online at Oxford Journals and will be in Aug. 1 print editions of the Journal of the National Cancer Institute.

Among its key findings:

Breast-cancer rates climbed 26 percent from the early 1980s to the early 1990s, then rose an additional 15 percent through 2001. From 2003 to 2006, the rate dropped 18 percent.

The rise in breast-cancer rates through the 1980s paralleled rises in mammography screening and hormone therapy, particularly use of estrogen plus progestin.

The 15 percent rise in breast-cancer rates from 1992 to 2002 mirrored the rise in hormone therapy; mammography screening, meanwhile, remained at 1991 levels.

The steep decline in breast-cancer rates that began in 2003 paralleled a 75 percent drop in hormone-therapy use, while mammography rates stayed the same.

The cancer-rate patterns showed up, largely, in women who were older than 45 and who had estrogen receptor-positive cancers — the types most sensitive to hormones.

Glass, senior investigator at the nonprofit Center for Health Research in Portland, and colleagues from the National Cancer Institute, reviewed the histories of 7,386 women diagnosed with invasive breast cancer and treated at Kaiser Permanente Northwest from 1980 to 2006. Kaiser’s data systems enabled researchers to trace connections between the health plan’s tumor registry and its clinical, pathology and pharmacy data to discover links between breast-cancer rates and types, mammography and hormone therapy.

Doctors have long known that breast cancer is sensitive to hormones. For instance, some patients with estrogen-sensitive breast cancer who were given such anti-hormones as tamoxifen saw their tumors shrink.

But it wasn’t until recently that scientists began to suspect that if physicians gave healthy women synthetic hormones, the drugs might trigger breast cancer. The disease takes years to develop, and hormones aren’t the sole culprit, Glass said. But hormones appear to encourage cancer to grow.

“The last step,” he said, “may be whatever stimulation is generated by the hormones.”

If you stop those hormones, Glass said, “the major risk goes away. It’s the most likely explanation for why rates dropped recently.”

The North American Menopause Society estimates that nearly 40 million U.S. women are of menopausal age, 40 to 58 years old. Some make the natural transition with little trouble, but others suffer miserable symptoms ranging from frequent hot flashes and night sweats to sleeplessness and vaginal dryness.

For decades, hormone-replacement medications helped many women endure, and they had added benefits: Those taking them showed up with lower rates of osteoporosis and colon cancer, for instance.

But in 2002, researchers dropped a bomb: Three years before it was supposed to end, the National Institutes of Health stopped a major clinical trial studying the risks and benefits of combined estrogen and progestin in healthy menopausal women when they discovered an increased risk of invasive breast cancer. The large trial, part of the Women’s Health Initiative, also found increases in coronary heart disease, stroke and pulmonary embolism in participants on estrogen plus progestin compared to women taking placebo pills.

Since then, doctors and patients have scoured the medical and natural landscape for alternatives.

Some physicians still prescribe synthetic hormones to women with severe symptoms and no other apparent breast-cancer risks, but they opt for lower doses, taken for shorter periods of time — no longer than five years. And some local, rather than systemic, hormones can alleviate such symptoms as vaginal dryness, said Dr. Jan Leigh, a Kaiser Permanente obstetrician/gynecologist.

Researchers have found little evidence that such popular, natural treatments as soy and red clover extracts stop hot flashes. Leigh said that drinking a couple of cups of soy milk each day seems to help some of her patients, and she doesn’t see any harm in that remedy. But other popular alternative therapies, such as black-cohosh supplements, which can stimulate estrogen receptors, have been less studied; their safety over the long term, she said, is unknown.

Leigh suggests that simple lifestyle measures help many women: dressing in layers; keeping a fan nearby; avoiding food or drink, such as red wine; that can trigger hot flashes.

“A lot of women can cope,” Leigh said, “once they understand what’s going on.”


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