They found in laboratory tests that the drug stimulated the growth of ovarian cancer cell lines to a degree that was similar to stimulation by estrogen. The finding raises concerns that, in contrast to its use as a safe alternative estrogen replacement therapy (ERT) in women who have had breast cancer, Raloxifene may not be a good alternative for ovarian cancer patients whose tumours are estrogen positive (ER+).
Raloxifene is one of the class of drugs known as SERMs (selective estrogen receptor modulators).
It has favourable estrogen-like effects on bone and on markers for cardiovascular disease, but is anti-estrogenic in human breast cancer cells and does not stimulate the uterine lining of postmenopausal women. This means that it encompasses the positive effects of ERT without the downside of increasing the risk of breast and endometrial cancer.
However, the drug's effect on ovarian cancer is unknown, Dr David Tourgeman told the European Society of Human Reproduction and Embryology annual meeting in Lausanne today (Tuesday 3 July).
His team at the University of Southern California-Keck School of Medicine in Los Angeles had subjected cells from an ER+ adenocarcimona of the ovary to an amount of Raloxifene equivalent to the normal 60mg oral dose. They found that it acted as an agonist, stimulating proliferation of the cells.
Dr Tourgeman, who is Assistant Professor of Obstetrics and Gynaecology, said: "To our knowledge, this is the first time that the effect of Raloxifene on ovarian cell lines has been evaluated. Currently, there is much debate among oncologists whether the presence of estrogen receptors on ovarian cancers necessarily means that estrogen itself will stimulate the growth or reappearance of the tumour, and ovarian cancer is not generally considered a contraindication to prescribing ERT.
"But, as up to 60% of epithelial ovarian cancers and a smaller percentage of anaplastic or recurrent ovarian cancers will be ER+, the most appropriate approach would be one of caution. In contrast to the clinical management of women with a history of breast cancer, Raloxifene may not be a good alternative to ERT in women with ER+ ovarian cancer."
But, Dr Tourgeman stressed, it was extremely important not to downplay the benefits of ERT on bone, cardiovascular protection and cognition.
"To withhold ERT from patients with a history of ovarian cancer because of these findings would be premature."
He said that these findings should serve as an impetus to epidemiological studies evaluating the effects of both estrogen as well as Raloxifene on ovarian cancer. The investigators are evaluating the effects of Raloxifene on other types of ovarian tumours.
Abstract no: O-161
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