Breast cancer survivors who took hormone therapy for menopausal symptoms had many more cancer recurrences than women who did not take hormones, a new study has found.
The study, conducted in Sweden, was halted abruptly when the difference between the groups became apparent because the researchers judged that even short-term use of the hormones carried an "unacceptable risk."
Although previous studies had shown an increased risk of breast cancer in healthy women who took hormones, the new report describes the first controlled experiment to study the drugs in breast cancer survivors.
Researchers say the findings mean that women who have had breast cancer should avoid hormones and find other ways to treat menopause symptoms.
That conclusion is just one more piece of bad news about hormone therapy, which has also been linked to increased risks of heart attacks, blood clots and strokes. Once widely promoted to keep women young and healthy, hormones were subsequently found to heighten the risk of some of the very conditions they were supposed to prevent. Now women are advised to take the lowest dose for the shortest time possible, and packaging carries a "black box" warning, required by the Food and Drug Administration.
Hormone use has dropped sharply since July 2002, when a large study in the United States called the Women's Health Initiative was stopped ahead of schedule because it detected an increased risk of breast cancer in women who took Prempro, a widely used hormone combination. Before the study, about 6 million women a year were using combination hormones; after it was published, the figure dropped by more than half.
Part of the health initiative, a study of women taking estrogen alone, has been allowed to continue because so far no serious adverse effects have been found. Results are expected next year.
The new study included 345 women who had been treated for breast cancer, had no recurrence and had severe menopausal symptoms such as hot flashes or night sweats.
Assigned at random, 174 women received hormones and 171 did not. After a median follow-up of 2.1 years, 26 women taking hormones had a recurrence or a new breast cancer, as opposed to seven not taking hormones. Most of those with recurrences had taken the hormones for two years or less; most were taking them when the tumors were diagnosed.
Most of the women in the Swedish study took both estrogen and progestin - similar to the most widely prescribed combination in the United States. A smaller group, those who had had hysterectomies, took estrogen alone. But not enough women were studied to determine whether there was any difference in risk between estrogen alone and the combination.
A report on the study is being published online today by the Lancet (www.thelancet.com) and in this Saturday's print version of the journal.
In a telephone interview, the director of the study, Dr. Lars Holmberg of University Hospital in Uppsala, said, "The steering committee of the trial was very worried when we saw the figures."
Dr. Rowan T. Chlebowski, chief of medical oncology at the Harbor-University of California, Los Angeles Medical Center, said, "Three-fold is a tremendous increase in breast cancer risk."
The study had some shortcomings, the researchers said, noting that the numbers were small and that a similar study, also in Sweden, did not find an increase in cancer recurrence linked to hormones. Researchers did not know why, but the second study was halted anyway when Holmberg's findings became known.
In a commentary accompanying Holmberg's report in the Lancet, Chlebowski said that the findings were still strong enough to use as a basis for advising breast cancer survivors to avoid hormones.
Dr. Larry Norton, a breast cancer expert at Memorial Sloan-Kettering Cancer Center in New York, said the results were no surprise.
"Breast cancer is clearly related to estrogen exposure," he said. "Many cases are estrogen-dependent."