Tibolone acts like the female hormones estrogen and progesterone in relieving menopausal symptoms. The new findings indicate that the drug should not be prescribed to any woman with known, past, or suspected breast cancer, said Prof. But, unlike estrogen and progesterone, it has been believed that tibolone would reduce the risk of some cancers.

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. This study included almost 3,100 women who'd had surgery for breast cancer. That meant that women taking tibolone had a 40% increased risk of recurrent cancer.. Among the 1,556 women taking tibolone, 237 (15.2%) experienced a cancer recurrence, compared with 165 (10.7%) of the 1,542 women taking the placebo. The women were randomly assigned to receive either 2.5 milligrams of tibolone a day or a placebo. 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. Many breast cancer patients use the drug to counteract the effects of giles menopause caused by cancer treatments.

Peter Kenemans, of the VU University Medical Center in Amsterdam, Netherlands, and colleagues.