December 14, 2006

Sharp Drop In Breast Cancer Incidence Attributed To HRT Decline
(Reuters Health)

After 20 years of a slow and steady increase in incidence of breast cancer, the incidence began dropping at about 1% per year in 1998. However, in 2003, there was a sharp decrease in incidence of 7%, which researchers at the 29th annual San Antonio Breast Cancer Symposium attribute to the decline in hormone replacement therapy use among postmenopausal women.

The steepest decline in breast cancer incidence occurred among women between 50 and 69, lead investigator Dr. Peter M. Ravdin of the University of Texas, M. D. Anderson Cancer Center, Houston, told meeting attendees.

Dr. Ravdin's team used the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) database to assess the incidence of breast cancer in the United States.

They found a slow increase in breast cancer incidence of approximately 1.7% per year between 1990 and 1998. Between 1998 and 2003, the incidence began to decrease for the first time, at approximately 1% per year.

In 2003, the marked decline was due to a 5.5% drop of in situ cancers and a drop in malignant cancers of 7.3%. Subset analysis showed a decrease in breast cancer of 6% during the first half of 2003 and a 9% decrease in the second half of that year.

Compared with 2000-2001, in 2003 there was a 1% decline among women in their forties, a decline of 11% for women in their fifties and sixties, and a 7% drop in breast cancer incidence for women in their seventies.

There was an 8% decline estrogen receptor-positive breast cancers and a 4% decline in estrogen receptor-negative tumors. For women in their fifties and sixties, there was a 12% decline in estrogen receptor-positive tumors compared with a drop of 4% in estrogen receptor-negative tumors.

The decline in breast cancer incidence coincided with the publication of the Women's Health Initiative study results, linking the use of hormone replacement therapy after menopause to an increase in breast cancer risk, as well as an increased risk of heart disease. When the trial was halted in 2002, about half of the women in the trial stopped taking HRT, Dr. Ravdin said.

"The possibility of the effect (of HRT and breast cancer risk) is much greater than originally thought," Dr. Ravdin said in an interview with Reuters Health after his presentation.

Dr. Ravdin sounded a cautionary note. "This is just what we think, of course, because epidemiology can never prove causation," he said. Another point is that this has the right "signature of HRT" as the explanation for the decline in incidence. "It occurred in women in their fifties and sixties, and that's exactly the population that was taking HRT."

The WHI is continuing to study these women after discontinuation of HRT. That should help to confirm, in part, the link between HRT and breast cancer incidence, Dr. Ravdin said.

Copyright © 2006 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.