This study included almost 3,100 women who'd had surgery for breast cancer. The new findings indicate that the drug should not be prescribed to any woman with known, past, or suspected breast cancer, said Prof. Many breast cancer patients use the drug to counteract the effects of jaime menopause caused by cancer treatments. Among the 1,556 women taking tibolone, 237.

The women were randomly assigned to receive either 2.5 milligrams of tibolone a day or a placebo. But, unlike estrogen and progesterone, it has been believed that tibolone would reduce the risk of some cancers. Tibolone acts like the female hormones estrogen and progesterone in relieving menopausal symptoms.

Peter Kenemans, of the VU University Medical Center in Amsterdam, Netherlands, and colleagues. -- A large study of tibolone, a drug used to treat menopausal symptoms and to prevent osteoporosis, was halted haskell after researchers found that the synthetic steroid significantly increased the risk of recurrent breast cancer among survivors of the disease. The women's mean age at the start of the study was 52.7 years and the mean time since surgery was 2.7 years.

Tibolone, brand name Livial, isn't available in the United States but is approved in 90 countries for easing menopausal symptoms and approved in 55 countries as an osteoporosis treatment.