The magnitude of change in serum prostate-specific antigen (PSA) after 5α-reductase inhibitor therapy may be useful in diagnosing prostate cancer in men with a prior negative biopsy and persistently increased or fluctuating PSA levels, researchers report in The Journal of Urology (2012;188:757-761).
“At a time when the value of PSA is being increasingly debated, we have shown that when used in a specific way, it can be of great value in identifying men with previously undetected prostate cancer,” commented lead investigator Steven A. Kaplan, MD, in a statement describing his team’s findings.
Kaplan is the E. Darracott Vaughan, Jr., Professor of Urology at Weill Cornell Medical College and director of the Iris Cantor Men’s Health Center at New York-Presbyterian Weill Cornell, both in New York, New York. He and his colleagues conducted a two-phase study involving a total of 276 men with PSA greater than 4 ng/mL or a PSA velocity change of 0.75 ng/mL and a normal digital rectal examination. All participants had previously undergone a minimum of two biopsies with no prostate cancer detected.
Each man was given 5 mg finasteride or dutasteride daily. Both agents are 5α-reductase inhibitors, designed to reduce the size of an enlarged prostate. The investigators theorized that if PSA remains high even after the prostate has shrunk, or if PSA rises after having reached its lowest level, cancer could be present. In addition, a biopsy can be more effective when the prostate gland is smaller.
The 97 men in phase 1 had PSA measured at 6 and 12 months, with repeat transrectal ultrasonography and biopsy (12 cores) performed at 1 year. At the 1-year mark, PSA fell by 2.4 ng/mL and prostate volume had decreased by 7.1 mL among these patients. Prostate cancer was detected in 27 of the men (27.8%), and the mean minimum PSA velocity from a nadir of 0.4 ng/mL was 0.6 ng/mL.
The phase 2 participants consisted of 179 men who underwent biopsy triggered by a change in nadir PSA of more than 0.4 ng/mL. A total of 48 of these men (26.8%) underwent repeat biopsy at a mean of 14.6 months, and 26 members of that subgroup (54.1%) were found to have prostate cancer. Among the 26 men with prostate cancer, 20 (76.9%) were found to have a Gleason score of 7 or greater, representing high-grade tumors.
“We have shown that using PSA with these drugs [finasteride and dutasteride] can help us differentiate prostate cancer from benign prostate disease in patients who are difficult to diagnose,” stated Kaplan. “It also demonstrates a better way to use both the PSA test and these powerful drugs.”