The Food and Drug Administration said Monday it is investigating the safety of a family of drugs known as gonadotropin-releasing hormone agonists, which are used for hormone deprivation therapy to treat men with prostate cancer. The agency said small studies have suggested that the drugs might be associated with an increased risk of diabetes and cardiovascular disease, although the evidence is not conclusive and agency scientists are still investigating.
The drugs, commonly called GnRH agonists or luteinizing-releasing hormone agonists, suppress the production of testosterone, the male hormone that stimulates the growth of many prostate tumors, by the testicles. Producing what is called chemical castration, they are an alternative to surgical castration, which is also used. They are not a cure for prostate cancer, but can significantly slow tumor growth or even shrink tumor size. Some of the drugs are also used by women to manage pain caused by endometriosis, to improve anemia associated with uterine fibroids before a hysterectomy and for palliative treatment of advanced breast cancer. They are also used in some children to treat a form of precocious puberty. There is no evidence suggesting an increased risk in women or children, the agency said.
Most of the studies reviewed by the FDA reported small but statistically significant increased risks of diabetes and heart disease, the agency said. But the data have a variety of shortcomings, including poor definition of what types of androgen deprivation therapy were used, the amount of drug used and for how long, and a lack of data about the patients' risk factors for the disease before therapy began, among other problems. Those deficiencies made it difficult to establish a cause-and-effect relationship.
While the FDA investigates the drugs, it said that patients should not stop taking them. Physicians planning to prescribe them should evaluate the risks and benefits and, when they are prescribed, monitor the patients for precursors of diabetes, as well as high blood pressure, high cholesterol and increased weight gain.
The drugs involved include:
-- Lupron, manufactured by Abbott Laboratories of Abbott Park, Ill.
-- Eligard, manufactured by Sanofi-Aventis of Bridgewater, N.J.
-- Synarel, manufactured by Pfizer of New York City
-- Trelstar, manufactured by Watson Pharmaceuticals of Corona
-- Vantas, manufactured by Endo Pharmaceuticals of Chadds Ford, Penn.
-- Viadur, manufactured by Bayer Pharmaceuticals of Wayne, N.J.
-- Zoladex, manufactured by AstraZeneca of Wilmington, Del.
This year, an estimated 203,415 new cases of prostate cancer will be diagnosed and about 28,372 men will die from it, according to the Centers for Disease Control.
-- Thomas H. Maugh II