Drugs for benign prostate tumors increase the risk of aggressive cancers, FDA says [Updated]
The Food and Drug Administration said Thursday it will require changes in the labeling of a family of drugs used to treat benign prostate hyperplasia to indicate that the drugs increase the risk of developing a more aggressive form of prostate cancer.
FOR THE RECORD: A sentence in this post which said, “For use in treating prostate cancer, the FDA said, the benefits of the drugs far outweigh the risks,” has been corrected to read, “For use in treating benign prostate hyperplasia, the FDA said, the benefits far outweigh the risks.”
The family of drugs are called 5-alpha reductase inhibitors, or 5-ARIs, and includes finasteride ( Proscar) and dutasteride ( Avodart), as well as the hair-growth drug Propecia. Dutasteride is also sold in combination with tamsulosin under the brand name Jalyn. The drugs are also increasingly used as a preventive agent for men who are at high risk of developing prostate cancer, but they are not approved for that purpose.
The drugs interfere with the production of male hormones, starving the tumors of nutrients they need to grow. For use in treating benign prostate hyperplasia, the FDA said said, the benefits far outweigh the risks.
The FDA’s concern is based on two studies in which the drugs were used to prevent the occurrence of prostate cancer in men who are at high risk of the disease. The two studies, one on finasteride in 2003 and one on dutasteride in 2010, showed that each of the drugs could reduce the risk of developing prostate cancers by about a quarter.
But the studies also found that the drugs appeared to increase the risk of developing the most aggressive form of prostate cancer, called high-grade prostate cancer — from 1% to 1.8% in one study and from 0.5% to 1% in the other. But why that occurs has been a source of great controversy. While some researchers believe that the drugs actually promote the development of the high-grade tumors, others argue that shrinkage of the swollen prostate gland simply makes those aggressive tumors more easy to detect. In its changes on the label of the drugs Thursday, the agency apparently decided to come down on the side of conservatism.
The agency included Propecia in the labeling changes even though that drug has not been directly linked to an increase in tumor formation. Propecia has a much lower concentration of finasteride than does Proscar and is thus thought to be safer.
In March, GlaxoSmithKline, which manufactures Avodart, said it would no longer seek approval to market the drug for the prevention of cancer because of the concerns. That followed a December meeting where an FDA advisory panel recommended against approving the drug for that purpose. Proscar and Propecia are marketed by Merck & Co.
The labeling changes do not apply to another family of drugs used for treating benign prostate hyperplasia. Those drugs are called alpha-blockers, and include tamsulosin (Flomax) doxazosin (Cardura), terazosin (Hytrin), alfuzosin (Uroxatral) and silodosin (Rapaflo). These drugs have not been show to reduce the risks of urine retention or surgery associated with an enlarged prostate.
