Their findings, published Tuesday by The Lancet medical journal, add to the already solid evidence that using hormone replacement to control menopausal symptoms, such as hot flashes and prevent brittle bone disease, carries significant health risks.
Eighteen months ago, U.S. government scientists abruptly ended the nation's biggest study of HRT using the combined hormones estrogen and progestin, saying long-term use significantly increases women's risk of breast cancer, strokes and heart attacks. That study involved older women who were well past menopause.
Last year, a British study concluded that women receiving HRT had a 22 percent higher risk of death from breast cancer than women who were not, and that those who used estrogen and progestin together had a markedly higher risk than those who used estrogen alone.
The Scandinavian researchers, led by Dr. Lars Holmberg from University Hospital in Uppsala, Sweden, had intended to follow their patients for five years.
They said they called off the study on Dec. 17 based on results from 345 women they had been following for an average of two years. Half the women were given HRT and the other half the best non-hormonal treatment for menopausal symptoms.
In the HRT group, 26 women had a recurrence or a new case of breast cancer. That compared with seven women among those who took the other treatment.
Unlike earlier studies, the Scandinavian trial did not find a significant risk difference between types of hormone treatments.
The trial was terminated because breast cancer survivors on hormone therapy experienced "an unacceptably high risk" of recurrence, the researchers wrote.
Two U.S. scientists unconnected with the trial — Dr. Rowan Chlebowski of Harbor-UCLA Research and Education Institute in Los Angeles County, and Dr. Nananda Col of Brigham and Women's Health Hospital — said "alternative safe and effective strategies for the difficult problem of menopausal symptoms in these women now need to be developed."
Dr. Steven R. Goldstein, professor of obstetrics and gynecology at New York University Medical Center, said the Scandinavian findings were "very significant" because it was the first randomized clinical trial in this subject and therefore more valid statistically than other recent studies suggesting it was safe for a women with a history of breast cancer to be on hormone replacement therapy.
"Obviously the pendulum is swinging the other way, and physicians will have to reconsider giving HRT to these patients," he said.