A drug used as hormone replacement therapy may actually encourage the growth of some kinds of ovarian cancer.

Laboratory tests on cancer cells found that Raloxifene, a commonly-prescribed drug in the UK, stimulated growth in those sensitive to the effects of the female hormone oestrogen.

To our knowledge, it is the first time that the effect of Raloxifene on ovarian cell lines has been evaluated

Dr David Tourgeman

The drug is given to help women who have had their ovaries removed in an effort to beat the cancer, and are subsequently vulnerable to post-menopausal problems such as bone-thinning.

Now, however, there is the suggestion that it might, in some cases, accelerate the re-growth of cancers from any cells left behind by treatment.

Doctors say it would therefore be unwise for any woman with an "oestrogen positive" ovarian cancer, in which the cells have "receptors" which are sensitive to the hormone, to be given the drug.

The warning was sounded at the European Society of Human Reproduction and Embryology conference in Lausanne.

Dr David Tourgeman, an assistant professor of obstetrics and gynaecology at the University of Southern California-Keck School of Medicine in Los Angeles, took cells from an ovarian cancer and exposed them to the same concentration of Raloxifene that might be produced by a standard 60mg dose.

Fast growth

He found it caused the cells to proliferate, growing faster than they would under normal conditions.

Dr Tourgeman said: "To our knowledge, it is the first time that the effect of Raloxifene on ovarian cell lines has been evaluated.

"Currently, there is much debate amongst oncologists whether the presence of oestrogen receptors on ovarian cancers necessarily means that oestrogen itself will stimulate the growth or reappearance of the tumour, and ovarian cancer is not generally considered a contra-indication to prescribing oestrogen-replacement therapy."

However, he said that as many as 60% of some kinds of ovarian tumours would be responsive to oestrogen, and that a cautious approach was necessary.

"Raloxifene may not be a good alternative to oestrogen-replacement therapy in women with oestrogen positive ovarian cancer."

Even with this mind, he said, it might be premature to withhold completely oestrogen-replacement therapy from patients, as the benefits for bone density and heart protection were considerable.