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Hormone Therapy Linked to Breast Cancer

CancerWise - June 2007

An extended analysis of cancer rates reinforces a strong association between use of hormone replacement therapy (HRT) and increased breast cancer incidence.

Significance of results

A decline in prescriptions written for supplemental hormones mirrored breast cancer rates that began to fall in 2002, continued to fall through 2003 and stayed low in 2004, according to M. D. Anderson researchers. Breast cancer incidence in 2004 was the lowest rate seen since about 1987.

The extended analysis was published in the April 19 issue of the New England Journal of Medicine by the study’s lead author Peter Ravdin, M.D., Ph.D., a research professor in M. D. Anderson’s Department of Biostatistics, and Donald Berry, Ph.D., professor and head of the Division of Quantitative Sciences.

Because their study was based on population statistics, the researchers cannot say for certain that HRT use is linked to development of breast cancer in some women, but add that it is the strongest explanation.

Background

The incidence of breast cancer has been steadily increasing in the past several decades, and so has the use of HRT (a combination of estrogen and progestin hormones), according to the analysis.

By the early part of this decade, about 30% of women 50 years of age and older used HRT, Ravdin says.

But half of those women quickly abandoned the agents in July 2002, when a large federal study found that women who used HRT were at significantly higher risk of developing breast cancer than women who didn’t.

That was the first large-scale study to suggest that these hormones might be fueling breast cancer growth. Based on those findings, Ravdin and Berry looked at breast cancer rates in the following months and years.

They presented preliminary findings on declining breast cancer incidence rates in 2002 and 2003 last December at a scientific meeting. An extended analysis that included the 2004 rates was published in April in the New England Journal of Medicine.

Research methods

Researchers at M. D. Anderson, the National Cancer Institute (NCI) and Harbor UCLA Medical Center analyzed data collected from the NCI that report on 9% of the U.S. population.

Primary results

The most significant results involved women with estrogen-receptor positive breast cancer (ER-positive) − tumors that use estrogen to fuel their growth.

Data showed breast cancer incidence declined:

  • By 6.7% in all women between 2002 and 2003
  • Primarily in women 50-69 years old
  • By 14.7% in women with HER2-positive breast cancer

Secondary results

Reseearchers also reported that:

2002 – Twenty million fewer HRT prescriptions were written.

2003 – The decrease in HRT may have prevented 14,000 incidences of breast cancer.

The researchers say their study cannot answer the question of whether stopping use of HRT leads to a temporary or permanent decline in breast cancer incidence. They also say that other factors may play a contributing role, including the possibility that fewer women had a mammogram during 2002-2004.

What’s next?

Ravdin and Berry stress that their results do not mean that all women should stop use of HRT.

“The risk of developing breast cancer from use of these hormones is relatively small and for some women with postmenopausal symptoms, the benefits of HRT are well worth that risk,” Ravdin says. “This is just another small piece of the puzzle to help women gauge the risks and benefits of using HRT.”

– From staff reports

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© 2014 The University of Texas MD Anderson Cancer Center