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The number of cases of breast cancer dropped by 7 percent in 2003, that's about 14,000 fewer women getting breast cancer than the year before. Researchers say the drop may reflects the fact that huge numbers of women stopped taking hormone replacement therapy the year before. The new analysis was reported yesterday at a meeting of breast cancer experts in San Antonio, Texas. The study is based on figures collected from cancer registries around the country.

Joining us now is Dr. Eric Winer, who directs the Breast Oncology Center at Boston's Dana-Farber Cancer Institute. And thank you for joining us this morning.

Dr. ERIC WINER (Director of Breast Oncology Center, Dana-Farber Cancer Institute): Sure. Thanks for having me.

MONTAGNE: Doctor, you chaired the session where this was presented, how impressive are these numbers?

Dr. WINER: I think the numbers are quite impressive. Just standing alone the fact that breast cancer incidents decreased in 2003 was quite exciting.

MONTAGNE: And this drop in cases coincides with a big drop in women taking hormones. So is that a real solid link?

Dr. WINER: I think one would be hard pressed to say that it's absolutely solid, but it's certainly very plausible. Most of the drop occurred in women over 50, women who might have been taking hormones and in the incidence of estrogen fueled or estrogen sensitive breast cancers. We know actually that when we use drugs that block the affective hormones in women who have breast cancer, their breast cancers can actually not grow or shrink in many cases in the course of a few months.

So it doesn't surprise a lot of people that withdrawing estrogen, or in some cases estrogen and progesterone, would result in a tumor that might have been detected in 2003 shrinking or in some cases perhaps even going away as a result of withdrawal of these hormones. Finally, the researchers that looked at this looked to see if there were other plausible explanations, and while there are some theories, this is really the most likely source of the change.

MONTAGNE: Just briefly remind us why women stopped taking hormone replacement therapy.

Dr. WINER: Well, so in 2002, studies came out that indicated, and indicated pretty definitively, that the long-term use of hormone replacement therapy, particularly combination therapy with estrogen and progestin, did not seem to convey the health benefits that people had once thought that they would. Now, these drugs for a long time have been known to increase the risk of breast cancer at least to a modest extent. But before 2002, it was thought that the risk were more than offset by other health benefits.

MONTAGNE: The other possible explanations, what might they have been for this drop?

Dr. WINER: During this time, there was apparently a slight decrease in the use of mammography and that was considered, but it's hard to imagine that that decrease could lead to this really fairly dramatic drop in incidents. For that matter, drugs like raloxifene or what's commonly called Avista, a drug that's used for osteoporosis, is also a drug that actually decreases breast cancer risk. And for many years, more and more women were taking that drug. But again, it's going to be a very important to see if these findings hold up over the next few years.

MONTAGNE: Again, this study was done by?

Dr. WINER: Researchers at the Andy Anderson Cancer Center in Houston.

MONTAGNE: The drop that was recorded here was so sudden, but doesn't cancer take years to develop? Is anyone saying that hormone replacement therapy is causing breast cancer?

Dr. WINER: I don't think anyone's suggesting here that this sudden drop is because cancers that would have arisen in subsequent years didn't arise at all. So being on estrogen or on a combination of estrogen and a progestin for some women might actually accelerate the growth of cancers. And by stopping that treatment, it is the equivalent of taking one's foot off the accelerator, in this case the estrogen accelerator.

And as a result of that, the cancer that could have been diagnosed in 2003 would potentially stop growing or in many cases might shrink. Now whether or not that cancer ultimately would re-grow and be diagnosed in the years ahead is something that we can speculate about but can't say for sure.

MONTAGNE: Dr. Winer, thanks for joining us.

Dr. WINER: Thank you very much.

MONTAGNE: Dr. Eric Winer directs the Breast Oncology Center at Boston's Dana-Farber Cancer Institute.

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