The National Institutes of Health (NIH) this week announced a significant drop in new breast cancer diagnoses, citing the decline in hormone replacement therapy (HRT) as the likely contributing factor. HRT prescriptions have declined by two-thirds since the findings that linked their use to a higher incidence of breast cancer and correspondingly, breast cancer incidence in women over the age of 50 has decreased by 9 percent. The decline has been most noticeable in women at risk of estrogen receptor (ER) positive tumors that need estrogen in order to grow and multiply. In analyzing what caused the drop in cancer diagnoses, several other possibilities were considered, including changes in reproductive factors, rates of mammography screening, environmental exposures, and changes in diet. However, HRT was the only risk factor that changed substantially from 2002 to 2003 and it does provide a possible explanation for the lower trend.
But others aren't so sure. The International Menopause Society advises caution in linking these two parallel trends observed in the US. They note that despite a similar decrease in the use of HRT in other countries, declines in the incidence of breast cancer were not recorded by other national cancer registries world-wide, such as in the UK. Additionally, they say that current knowledge of the biology of breast cancer suggests that a nearly 10 percent decrease in breast cancer incidence occurring within a year after cessation of estrogen therapy is unlikely.
The NIH also hedges its bets, with researcher Kathy Cronin cautioning that; "Recent reports have suggested a small decline in mammography use after 2000. Screening may play a role as well, and the contribution of mammography to the observed decline in incidence is currently being investigated."
The report notes that the flow-on effects of cessation of HRT are likely to be complex and the effects may vary depending on the type of HRT used and other factors specific to how the hormones affect the body. From the data in the NIH report, it seems that the decline in breast cancer incidence that is related to a nationwide decline in use of HRT may have has run its course, and breast cancer incidence rates may stabilize or even begin to rise again. Researchers do not yet know if this reduction in HRT use will have a long-term effect on rates, or whether reduction in hormone levels simply slowed the growth of clinically detectable tumors, in which case as HRT use stabilizes, breast cancer incidence will begin to rise again.
Summing up, Christine Berg, from the National Cancer Institute, said that decisions about the use of HRT are complex. "While HRT provides relief from the symptoms of menopause, it may also increase one's risk of breast cancer. It is important that women meet with their doctor to discuss what decision is right for them, particularly if they are at high risk for breast cancer," she concluded.
Related articles:
Long-Term HRT Poses Significant Breast Cancer Risk
HRT Cancer Risk May Have Been Overstated
Source: NIH/National Cancer Institute, International Menopause Society, University of Texas M. D. Anderson Cancer Center
