Fewer women are facing the diagnoses of breast cancer these days and the recent drop in hormone replacement therapy (HRT) is the most likely reason, according to new research.
In 2002, the Women’s Health Initiative study revealed a link between HRT and increased risk of breast cancer. A sharp drop in the number of women on long-term HRT followed the announcement. Between 2001 and 2004, there has been a 11.8 percent annual decline in breast cancer incidence and a 14.7 percent decline in estrogen receptor (ER) -positive invasive breast cancer.
Although the link between HRT and breast cancer may seem obvious, scientists hesitate to make such a claim without first gathering evidence. Some have suggested the reduced rate of women undergoing mammography in the same period may be an explanation.
Researcher Karla Kerlikowske, M.D., from the University of California, San Francisco, and her colleagues wanted to know what was behind the recent decline in invasive breast cancers. By studying a group of women who had all undergone mammographic screening, researchers were able to isolate other risk factors.
“In a screened population, you wouldn’t expect the rates to go down unless some risk factor changed,” Dr. Kerlikowske said. The rates of invasive breast cancer did go down in the study’s population of more than 600,000 women, leading study authors to conclude the decline in mammography rates is not a likely reason for the cancer decline. Rather, Dr. Kerlikowske said their results suggest the decline in HRT use contributed to the decline in breast cancer incidence.
Dr. Kerlikowske said the data also suggested the breast cancer risk for women on HRT dropped once they stopped taking hormones. “If your risk was increased, it will abate over time,” she said, adding further research is needed to uncover how much and how quickly breast cancer risks go down after HRT cessation.
SOURCE: Ivanhoe interview with Karla Kerlikowske, M.D.; Journal of the National Cancer Institute, 2007; DOI: 10.1093/jnci/djm111