Two studies have shown a link between hormone replacement therapy (HRT) and women’s cancers. One study, an extended analysis of data from the National Cancer Institute’s cancer registries, reinforces a strong association between the use of HRT and increased breast cancer incidence. Researchers at The University of Texas M.D. Anderson Cancer Center in Houston, TX, reported these resultsin the New England Journal of Medicine
. Another study, funded by Cancer Research UK and published online in Lancet
, shows that women whotake HRT are more likely to be diagnosed with ovarian cancer and to die of the disease.
The M.D. Anderson researchers studied breast cancer rates from 2002 to 2004 using the NCI’s Surveillance, Epidemiology and End Results registries. They found that breast cancer incidence dropped by 6.7% in 2003 and stayed at the same level in 2004. The investigators speculate that thesharp decrease in the use of postmenopausal HRT, which followed the results of the Women’s Health Initiative in mid-2002, correlates with the fall in new breast cancer diagnoses through 2003. The decrease was mainly found in women older than 50, and was seen mostly in estrogen receptor-positive cancer. ER-positive cancers fell by 14.7% , while there was a 1.7% decrease in ER-negative cancers.
The researchers looked at several other factors that could be responsible for the decrease in breast cancer. They looked for flaws in the data itself, changes in reproductive factors, changes in mammogram screening rates, changes in environmental exposures, changes in diet, and change sin the use of HRT. Only the use of HRT changed substantially, with 47 million prescriptionsin 2002 but about half as many in 2003.
The study does not suggest that decreasing HRT use would lower breast cancer incidence, the researchers caution. As a result, women should not stop their use of HRT, Peter Ravdin, MD, PhD, professor in the Biostatistics department at M.D. Anderson who led thestudy told Oncology & Biotech News
. Dr. Ravdin tells his patients that they should use the drug at the lowest dose and for theshortest time period to control hot flashes and other menopausal symptoms. “I think that current guidelines are reasonable,” said Dr. Ravdin. “Basically these guidelines say that, for difficulties with menopause, women may benefit from HRT but that there are risks associated with use and that to minimize these risks women should not take HRT uncritically for long periods.”
Further, the researchers said that their study cannot answer three key questions: whether stopping the use of HRT leads to a permanent or a temporary decline in breast cancer incidence; if this effect is seen with all types of HRT; and how much of a contributing role other factors may have played in the decline. “This is just another small piece of the puzzle to help women gauge the risks and benefits of using HRT,” Dr. Ravdinsaid.
paper, which shows a link between HRT and ovarian cancer, is based on results from the Million Women study, a UK national study of women’s health, involving around one million women aged 50 and over. The results show that there is one extra case of ovarian cancer in every 2,500 women who take HRT, and that there will be one additional death from ovarian cancer for every 3,300 women who take HRT. The researchers at Oxford University’s epidemiology unit who conducted the study estimated that use of HRT since 1991 has led to an additional 1,300 cases and 1,000 deaths from ovarian cancer.