Progestogen in HRT may be linked with increased breast cancer risk

Menopausal women who have had breast cancer who take hormone replacement therapy that contains both estrogen and progestogen may have an increased risk of breast cancer recurrence, according to a report in the April 6th issue of the Journal of the National Cancer Institute.

Two recent Swedish studies comparing menopausal hormone therapy with no menopausal hormone therapy in women with early-stage breast cancer reached different conclusions about the risk of breast cancer recurrence, the authors explain. Dr. Eva von Schoultz and colleagues from Karolinska University Hospital & Institute, Stockholm, reviewed the design of the two studies in an effort to understand why they had different outcomes.According to the authors, the principal difference was that the Stockholm trial attempted to minimize the use of progestogen combined with estrogen, whereas the HABITS trial did not.In the Stockholm trial, nearly three quarters of the women assigned to menopausal hormone therapy received estrogen alone or minimal exposure to progestogen. In this trial, hormone therapy was not associated with the risk of breast cancer recurrence.In contrast, many of the women in the HABITS trial received continuous combined treatment with estrogen and progestogen. The report indicates that hormone therapy in this trial was associated with a 3.3-fold increased risk of breast cancer recurrence.A greater percentage of women in the Stockholm trial (52%) than in the HABITS trial (21%) received tamoxifen, which, the investigators note, could also account for the difference in breast cancer recurrence.”Although it is tempting to speculate that treatment regimens with estrogen and a minimum of progestogen may be safe,” the researchers conclude, “the management of menopausal symptoms and quality of life for patients with breast cancer remains an important unsolved problem.””Because doses of estrogen and progestogen and treatment regimens may be associated with the recurrence of breast cancer, there is an urgent need to identify safe and effective strategies to manage menopausal symptoms and improve the quality of life for patients with breast cancer,” the authors add.”The results from these two trials, although limited by several design and implementation features, provide additional evidence that progestin use is associated with an increased breast cancer risk, compared with its nonuse,” write Dr. Rowan T. Chlebowski from UCLA Medical Center, Torrance, and Dr. Garnet L. Anderson from Fred Hutchinson Cancer Research Center, Seattle, in a related editorial.”The possibility that use of estrogen alone in symptomatic breast cancer survivors with a hysterectomy may represent an option with a favorable risk/benefit balance warrants further clinical attention,” they conclude.(Source: J Natl Cancer Inst 2005;97:471-472,533-535: Reuters Health: Oncolink: April 2005.)