Studies examine menopausal hormone therapy and risk of breast cancer recurrence

In 1997, two randomized trials, the Hormonal Replacement Therapy--Is It Safe? (HABITS) trial and the Stockholm trial, began in Sweden to test the effects of menopausal hormone therapy in women after they had been diagnosed with early-stage breast cancer. The HABITS trial, which ultimately included 434 breast cancer patients, was halted early in December 2003 because, at a median follow-up of only 2.1 years, the risk of breast cancer recurrence among women receiving hormone therapy was 3.3 times higher than the risk among women receiving no treatment.

Eva von Schoultz, M.D., Ph.D., and Lars E. Rutqvist, M.D., Ph.D., of the Karolinska Institute, in Stockholm, Sweden, and the Stockholm Breast Cancer Study Group now report the results of the Stockholm trial, in which 378 breast cancer patients were randomly assigned to receive either menopausal hormone therapy for 5 years or no treatment. The trial was similar to the HABITS trial but used a hormone therapy regimen that differed in composition and timing.

In the Stockholm trial, after a median of 4.1 years of follow-up, there was no association between hormone therapy use and the risk of breast cancer recurrence. The authors suggest that differences in the composition and timing of the hormone therapy used in the Stockholm trial could explain why the trial's results differed from those of the HABITS trial.

"Although it is tempting to speculate that treatment regimens with estrogen and a minimum of progestogen may be safe, the management of menopausal symptoms and quality of life for patients with breast cancer remains an important unsolved problem," the authors write. "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."

In an editorial, Rowan T. Chlebowski, M.D., Ph.D., of the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center in Torrance, Calif., and Garnet L. Anderson, Ph.D., of the Fred Hutchinson Cancer Research Center in Seattle, note that the results of these two trials provide additional evidence that use of combined estrogen and progestin is associated with an increased risk of breast cancer. However, they write, "the lack of direct evidence for the effects of estrogen alone from these two trials, especially in the context of divergent data on the effects of exogenous estrogen, emphasizes the need to design subsequent studies to address questions for specific agents."

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