Hair-loss drug interferes with prostate cancer test

Propecia found to interfere with cancer test results:
The hair-loss drug Propecia interferes with the most commonly used test for prostate cancer, causing inaccurate readings that can mask the presence of the disease, researchers reported Monday.

An estimated 4 million men worldwide use the drug, whose active ingredient is finasteride, which prevents the breakdown of testosterone. Researchers already knew that the high doses of finasteride in the prostate-enlargement drug Proscar could reduce levels of the marker called prostate specific antigen, or PSA.

The new study is the first to show the lower levels in Propecia also do so.

The suppression could mean that a previously safe reading on a PSA test could be false, said Dr. David Quinn, a medical oncologist at the University of Southern California who has worked on previous studies on finasteride and spoken for the drug's maker, Merck & Co., on other drugs but was not involved with this study.

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