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Study Strongly Links Hormone Therapy, Cancer

December 1, 2010
Written by: , Filed in: Breast Imaging
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A study of more than 2 million mammogram screenings shows a strong link between reduced hormone therapy and declines in both ductal carcinoma in situ (DCIS) and invasive breast cancer.

The link is so pronounced that the researchers think the evidence also suggests that hormones promote breast tumor growth.

Hormone therapy—a combination of progestin and estrogen—to alleviate postmenopausal symptoms soared in the 1980s and ’90s. The rate of breast cancer steadily increased as well. Then in 2002 came the first of several reports and studies indicating that the therapy was associated with higher risk of breast cancer and other potential health hazards. Postmenopausal women are now advised to avoid long-term hormone therapy or to use the lowest dose possible for the shortest time.

“We show that the incidence of breast cancer decreases if you take the hormones away,” said Karla Kerlikowske, MD, senior author of the new study. “The fact that we’re continuing to see a decrease in invasive cancer means that the effects of stopping the hormones may be long-lasting.”

Dr. Kerlikowske is professor of medicine and epidemiology and biostatistics at the University of California, San Francisco’s Helen Diller Family Comprehensive Cancer Center. She’s also codirector of the Women’s Veterans Comprehensive Health Center at the San Francisco VA Medical Center. She was quoted in a UCSF news release.

In the study, researchers reviewed 2,071,814 screening mammograms performed from January 1997 through December 2008 on nearly 700,000 women ages 40 through 79. Women 50 to 69—the age group that had the highest rate of hormone therapy—showed the biggest reduction in invasive breast cancer during the time period when hormone therapy began a steep decline. The rate dropped from 40 cancers per 10,000 mammograms in 2002 to 31 per 10,000 mammograms in 2005. Rates of DCIS also dropped markedly in the same group after advisories against hormone therapy began.

Cancer rates in women ages 70–79 showed similar declines.

Among women 40 through 49, who were less likely to have been on hormone therapy, breast cancer rates did not change during the course of the study.

The study’s authors say their findings suggest that hormones help promote the growth of preexisting but latent hormone-dependent cancers—both invasive and DCIS.

“The study supports the idea that by giving the hormones, we were promoting tumor growths,” said Dr. Kerlikowske. “When the promoter is taken away, the incidence of breast cancer decreases.”

She said short-term use of hormone therapy is “probably OK. But long term, it is not OK.”

The study was published online last month in the Journal of Clinical Oncology.

Related seminar: Breast Imaging and Digital Mammography

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