According to the results of a study published in the Journal of the National Cancer Institute, a sharp decline in the use of postmenopausal hormones was followed by a drop in the rate of breast cancer.
Postmenopausal hormone therapy with either estrogen alone or estrogen plus progestin effectively manages several common menopausal symptoms. However, large clinical trials conducted as part of the Women’s Health Initiative (WHI) raised concerns about the health risks of these therapies. In 2002, for example, it was reported that combined estrogen plus progestin increases the risk of breast cancer, heart disease, stroke, and blood clots. This report was followed by a rapid decline in the use of postmenopausal hormones.
The decline in use of postmenopausal hormones was followed by a drop in breast cancer incidence rates. A previous analysis of U.S. cancer rates reported that the rate of estrogen receptor-positive breast cancer (the type most likely to be linked with hormone use) dropped by 8% in 2003. Although other factors may have contributed to this drop, researchers concluded that the decline in use of postmenopausal hormones is likely to have played a major role.
To further explore the link between trends in breast cancer and trends in postmenopausal hormone use, researchers conducted a study within a managed care organization in Oregon. The researchers evaluated breast cancer trends between 1980 and 2006, along with trends in screening mammography and postmenopausal hormone use.
- Rates of breast cancer increased (with some fluctuations) from the early 1980s through 2001. There was a small drop in the breast cancer rate during 2001–2002, and then a sharp drop during 2003–2004. The rate during 2003–2004 was 18% lower than the rate during 2000–2001.
- The drop in the breast cancer rate was observed for both estrogen receptor-positive and estrogen receptor-negative breast cancer.
- The drop in the breast cancer rate did not appear to be explained by a decrease in screening mammography. Rates of mammography remained fairly steady during that time period.
- Use of postmenopausal hormones increased between 1988 and 2002 but then dropped by 75%. This sharp decline in use of postmenopausal hormones appears likely to explain at least some of the subsequent drop in breast cancer rates.
These results provide additional evidence that recent declines in breast cancer incidence may be due at least in part to a decline in the use of postmenopausal hormones. An unexpected finding from this study, however, was the decline in both estrogen receptor-positive and estrogen receptor-negative breast cancer. Postmenopausal hormones are thought to have the greatest impact on estrogen receptor-positive breast cancer. Other factors may also be influencing recent breast cancer trends.
Rossouw JE, Anderson GL, Prentice RL et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women’s Health Initiative randomized controlled trial. JAMA. 2002; 288:321-33
 Glass AG, Lacey JV, Carreon JD, Hoover RN. Breast cancer incidence, 1980-2006: combined roles of menopausal hormone therapy, screening mammography, and estrogen receptor status. Journal of the National Cancer Institute. 2007;99:1152-61.