Following a sharp decline in the early part of the 21st century, breast cancer rates are no longer falling in the United States, according to new data released Monday by the National Cancer Institute (NCI).

Researchers from the NCI found that while there was a drop of seven percent in new cases between 2002 and 2003, it did not keep falling between 2003 and 2007.

The dramatic drop between 2002 and 2003 was attributed to the drop in the use of hormone therapy. Many women turned away from hormone therapy that year after the Women's Health Initiative linked hormone treatment to an increased risk of breast cancer.

The researchers did not tease out the reasons for the change in the trend. They speculated that improvements in mammography may have had an effect on the numbers. And while hormone use has fallen over the years, the decrease after 2003 may not have been big enough to continually affect the incidence rate, they suggested.