New Study Reaffirms HRT Link to Breast Cancer Rate Decline

"When HRT went down, breast cancer rates went down and mammography rates remained the same," Glass said. "This was an important finding, because others had suggested maybe the drop in breast cancer rates was because mammograms had gone down, but it didn't happen in the Kaiser numbers. The only thing we can figure out is, it's probably related to HRT, that fluctuations in HRT are the most likely explanation for fluctuations in breast cancer rates."

The increase in breast cancer rates occurred primarily in women over the age of 45 who had estrogen receptor-positive breast cancer.

According to Glass, this study is the first to document all these different factors -- mammography, hormone therapy, breast cancer and estrogen-receptor status -- in one study.

But one expert found the study's conclusions lacking.

"This is an interesting look at the picture but really is not evidence-based medicine," said Dr. Lila Nachtigall, director of the women's wellness program at New York University Medical Center and professor of obstetrics and gynecology at New York University School of Medicine. The study did not correlate individual cases of breast cancer with hormone use, therefore issues of causality cannot be decided, she added.

"To try to prove causality is confusing to doctors and patients," she said. "I think it's a combination of things."

More information

For more on HRT, visit the U.S. National Library of Medicine.

SOURCES: Andrew Glass, M.D., senior investigator, Kaiser Permanente Center for Health Research, Portland, Ore.; Jay Brooks, chairman of hematology/oncology, Ochsner Health System, Baton Rouge, La.; Lila Nachtigall, M.D., director of the Women's Wellness Program at New York University Medical Center and professor of obstetrics/gynecology at New York University School of Medicine, New York City; August 2007,Journal of the National Cancer Institute