In 2002, a national study of millions of American women showed that taking hormone replacement therapy during menopause increases the risk of breast cancer, blood clots and strokes.  The news prompted many women to stop taking the medication.  Now another study has confirmed that when women stopped taking the hormone, breast cancer rates dropped. VOA's Melinda Smith has the latest.

The study -- published in the August issue of the Journal of the National Cancer Institute -- shows what happened when many women stopped taking Hormone Replacement Therapy, or HRT.  The results became apparent when millions of women went in for a yearly mammogram.

Dr. Karla Kerlikowske

Dr. Karla Kerlikowske authored the study. "If everybody's getting routinely screened, you'd expect cancer rates to be flat.  They shouldn't really change over time unless something happens in the population where risk factor changes."

At least 16,000 American women taking HRT had participated in a landmark study conducted over a period of years by the National Institutes of Health.  In 2002, that study was halted when a strong link was established between the hormone medication and breast cancer. 

Doctors and their patients got the message.  Use of Hormone Replacement Therapy -- a combination of estrogen and progestin -- dropped by 38 percent the following year. 

Now a new study by the National Cancer Institute reconfirms the effects of not taking the hormone medication. 

"We saw a drop in the agent that causes breast cancer, and with that a decline in invasive cancer, and importantly, estrogen receptive positive cancer," says Dr. Kerlikowske

The 13 percent drop in the breast cancer rate equates to about 17,000 fewer breast cancers diagnosed every year.  The research was based on at least 600,000 mammograms over a seven-year period of women aged 50 to 69.

While the latest study proves the relationship between the hormone use and breast cancer, Dr. Kerlikowske says it also poses more questions for the patients. "If you stop the hormones, does that mean the tumors regress completely that they've promoted?  Does that mean they just stop growing or does that mean they're just growing more slowly, so you'll detect them later in time?"

While there has been a lot of research about breast cancer conducted already, women's health experts say this is the first study to tie everything together:  mammography, hormone therapy and breast cancer