The rate of women developing breast cancer in the U.S. dropped 6.7% in 2003. Similar reports have come from Australia and Germany. Some researchers believe the unusual drop is related to the decreased use of hormone replacement therapy.
Hormone replacement therapy (HRT) involving estrogen and/or progestin was commonly given to alleviate severe hot flashes or night sweats in postmenopausal women up until 2002. At that time a highly publicized nationwide study, the Women’s Health Initiative (WHI), indicated an increased risk of breast cancer, heart disease, stroke and other ailments in some women undergoing HRT. Within two years, the most commonly forms of HRT in the US (Premarin and Prempro) dropped nearly one third from 61 million prescriptions per year to 21 million.
The National Institutes of Health reported that a study from the University of Texas M.D. Anderson Cancer Center documented a drop in breast cancer rates beginning in mid-2002 and leveling off by 2004. The decrease occurred only in women over the age of 50 (postmenopausal) and in the type of breast cancer that is stimulated by the presence of estrogen.
“Understanding the effect of cessation of HRT may be complex,” the NIH report admits. “Effects may vary depending on the type of HRT used and other factors specific to how the hormones affect the body” according to the study. Additional factors that could explain the drop in breast cancer rates include decreased mammogram screening since 2002, variations in environmental exposures, or changes in women’s diets.
The statistical analysis published by M.D. Anderson Cancer Center does not prove a cause and effect between the drop in breast cancer rates and the drop in HRT. Still, Christine Berg, M.D. from the NIH says that “While HRT provides relief from the symptoms of menopause, it many also increase one’s risk of breast cancer. It is important that women meet with their doctors to discuss what decision is right for them, particularly if they are already at high risk for breast cancer.
NIH News, 2007.