PSA test has higher accuracy for patients taking finasteride

New findings on finasteride from Prostate Cancer Prevention Trial

Finasteride increases prostate-specific antigen (PSA) testing's ability to detect prostate cancer, according to a study in the Aug. 16 Journal of the National Cancer Institute.

Doctors prescribe finasteride for men with enlarged prostates. The drug decreases prostate swelling and helps men with urinary problems. The Prostate Cancer Prevention Trial (PCPT) found that finasteride reduced a man's risk of prostate cancer by 25 percent but was associated with an increased number of high-grade tumors, making scientists worried about the effect of the drug.

Dr. Ian Thompson, of the University of Texas Health Science Center in San Antonio, and colleagues examined the PSA test's ability to detect prostate cancer in the PCPT in men taking finasteride or a placebo. The group studied the PSA test's sensitivity and diagnostic accuracy for both groups. Chen Chi, of the Southwest Oncology Group in the Public Health Sciences Division and Center affiliate Donna Ankerst, were the primary statisticians for the study.

The authors, who included PHS's Phyllis Goodman and Dr. Catherine Tangen, found that finasteride changed the diagnostic characteristics of the PSA test such that it detected prostate cancer with higher sensitivity and accuracy in men in the finasteride group than men in the placebo group. They suggest that at least part of the increased detection of high-grade prostate cancers in the finasteride arm of the PCPT may be related to finasteride's ability to improve the performance of the PSA test and not to the induction of high-grade disease.

The authors said, "This bias would be expected to contribute to greater detection of all grades of prostate cancer with finasteride."

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