New research from France suggests that certain forms of hormone replacement therapy (HRT) may significantly increase a woman’s risk for breast cancer during menopause. However, the caveat that not all types of HRT are associated with this increased risk may offer a bit of good news to women who currently use or are planning to begin hormone therapy.

There did appear to be a correlation between the length of treatment and increased breast cancer risk overall, regardless of the time point at which treatment was started.

The current study, led by Francoise Clavel−Chapelon at the Institut Gustave Roussy, Villejuif, France followed over 53,000 post−menopausal women, 1,726 of whom were diagnosed with breast cancer. They analyzed the type of hormone treatment used, if any, how long the women had been on HRT, and the time at which they started it. They compared the number of instances of breast cancer in women who used HRT and women who had not.

They found that among women who had begun estrogen−protestogen treatment within three years after beginning menopause and used the treatment for two years or less had a 54% increased risk of developing invasive breast cancer as compared to women who had never taken hormone supplements. However, when women had begun the treatment after three years post−menopause, the research team found no associated increase in the risk of breast cancer. There did appear to be a Correlational study between the length of treatment and increased breast cancer risk overall, regardless of the time point at which treatment was started.

Clavel−Chapelon notes that the results were different when progesterone, one of the varieties of progestogen, was used alongside estrogen. She says that “[t]his 54 percent increase in risk is an average, but does not seem to apply to estrogen−progesterone menopausal hormone therapy, for which no increased risk was observed when used two years or less, even close to menopause.” In other words, estrogen−progesterone therapy did not appear to increase breast cancer risk, no matter when women began the treatment.

Leslie Bernstein, editor of the Journal of Clinical Oncology in which the study was published, wrote an editorial published in conjunction with the study calling for a “conservative approach” until more research can be devoted to the issue. She suggests using hormone replacement therapy “briefly and only when menopausal symptoms are so intense that no other approach will work.” Women should clearly discuss with their doctors the risks and benefits associated with the various forms of treatment, in order to determine what type of therapy, if any, is right for them.

The study was published in the September 14, 2009 online edition of the Journal of Clinical Oncology.