LONDON, March 25 — Breast cancer survivors treated with hormone replacement therapy had a more than two-fold increased risk of recurrence or a contralateral malignancy, according to long-term follow-up data from a randomized clinical trial.
•Note that this is one of the few randomized, controlled studies that have examined the risk of breast cancer recurrence associated with HRT.
Those randomized to HRT had five-year breast cancer rates of 22.2% compared with 8% in women who received best patient care for menopausal symptoms without hormone therapy, Lars Holmberg, M.D., Ph.D., of King’s College London, and colleagues, reported in the April 2 issue of the Journal of the National Cancer Institute.
“The results of the HABITS [Hormonal Replacement after Breast Cancer — Is It Safe?] trial indicate a substantial risk a new breast cancer event among breast cancer survivors using hormone therapy,” the authors concluded.
“Our results further suggest that hormone therapy not only induces and promotes breast cancer but may also stimulate the growth of tumor microdeposits in breast cancer survivors,” they added.
Despite the statistically significant impact of hormone therapy on breast cancer risk, the authors said more data from randomized studies are needed to define the risk and to clear up inconsistencies in prior studies.
However, Kathleen Pritchard, M.D., a breast cancer specialist at Sunnybrook Odette Cancer Center in Toronto, said in an accompanying editorial that the study “suggests quite definitively that there is a statistically significantly increased risk of recurrence in women given HRT following diagnosis of breast cancer.”
Persistent questions about the potential risks and benefits of HRT in breast cancer survivors provided impetus for several observational studies and analyses of case series. More recently, data from the Women’s Health Initiative and the Million Women Study provided additional compelling evidence of an increased risk of breast cancer among HRT users, the King’s College authors said.