THURSDAY, June 7 (HealthDay News) -- More statistics from U.S. health officials confirm that rates of breast cancer have fallen since many women stopped using hormone-replacement therapy five years ago.

The trend was first reported in April in the New England Journal of Medicine, in a study that showed an 8.6 percent drop in breast cancer among postmenopausal women from 2001 to 2004. That decline coincided with a significant drop, starting in 2002, in the number of prescriptions for HRT, which had been linked to an increased risk for breast cancer.

Now, a new report in the June 8 issue of the U.S. Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report confirms these findings, using a much larger set of data.

Combining statistics from the U.S. National Cancer Institute's Surveillance, Epidemiology, and End Results program with the CDC's National Program of Cancer Registries program, the CDC was able to produce data that accounts for approximately 86 percent of the U.S. population.

The analysis showed that rates for invasive breast cancer dropped each year from 1999 to 2003. The greatest decrease (6.1 percent) occurred between 2002 and 2003. Moreover, women over age 50 had a significant decrease in breast cancer during this period.

In 2002, the Women's Health Initiative study reported that hormone-replacement therapy for menopausal and postmenopausal women was linked to a greater risk of breast cancer.

The new CDC statistics revealed a decrease in breast cancer from 2002 to 2003 in all women over 50 years of age, with women aged 60 to 69 showing the largest decrease. Also, women of all racial and ethnic groups had a significant decrease in breast cancer rates from 2002 to 2003, except for American Indian/Alaska Native women, whose breast cancer rates were stable.

At first glance, the new study appears to suggest that the drop in breast cancer rates is directly related to the drop in HRT use.

A study of California women aged 50 to 74 found that rates of HRT dropped by 68 percent from 2001 to 2003. During the same time, breast cancer rates dropped by 10 percent among the women in the study and 11 percent among all women in California.

But, since the rate of breast cancer started dropping before 2002 -- before the decrease in HRT use -- there may be other factors that might have contributed to the decline in breast cancer. These factors might include diet and lifestyle changes, according to an editorial note that accompanied the MMWR report.

More studies are need to confirm these findings, the editorial authors said.

More information

For more on preventing breast cancer, visit the American Cancer Society.

SOURCES: June 8, 2007, U.S. Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report; April 19, 2007, New England Journal of Medicine