By Michael Smith, North American Correspondent, MedPage Today
Published: August 09, 2012
Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco and Dorothy Caputo, MA, BSN, RN, Nurse Planner

The drugs used to treat benign prostatic hyperplasia (BPH) may also help detect some hard-to-find cases of prostate cancer, researchers reported.

In a two-part prospective study, treatment with 5α-reductase inhibitors enhanced the usefulness of prostate specific antigen (PSA) testing in men with persistently increased serum PSA but negative biopsy results, according to Steven Kaplan, MD, of Weill Cornell Medical College in New York City, and colleagues.

The magnitude of change in serum PSA after drug therapy may help to differentiate between men with cancer and those with BPH, Kaplan and colleagues reported in the September issue of the Journal Of Urology. In addition, the new screening method mainly detected high-grade tumors (Gleason score of 7 or greater).

PSA alone, Kaplan noted, is not a good indicator of the presence of prostate cancer, because it measures several factors — including enlargement of the prostate and inflammation — that are not exclusively linked to the disease.

On the other hand, PSA that remains high or rebounds from its lowest level could indicate cancer, even though the prostate has shrunk after 5α-reductase inhibitor therapy. Also, a biopsy could be more effective in a smaller gland.

To test those ideas, the authors enrolled 276 men for a two-phase study. In the first part, 97 men were given 5 mg of finasteride (Proscar) or 0.5 mg of dutasteride (Avodart) daily; had their PSA measured at 6 and 12 months; and had a transrectal ultrasonography and biopsy performed at 12 months.

In the second part, the remaining 179 men were given the same drug therapy, but only had a biopsy if their PSA rebounded from its lowest level by more than 0.4 ng/ml.

In the first part, the drugs reduced PSA levels by an average of 2.4 ng/ml (-46.7%) and prostate volume by an average of 7.1 ml (-17.9%).

On biopsy, 27 of the men were found to have cancer (27.8%) and the magnitude of their PSA reduction averaged 2.1 ng/ml — significantly less than the drop of 2.8 among the remaining 70 with BPH.

A key finding was that the average PSA rebound among men who had cancer was more than 0.4 ng/ml, Kaplan and colleagues reported.

For that reason, a rebound of that magnitude or greater triggered a biopsy in the second part of the study.

All told, 48 men in the second group had a biopsy after an average of 14.6 months of drug therapy and 26 (54.1%) were found to have cancer.

Most of those (20 or 76.9%) had disease with a Gleason score of 7 or greater, Kaplan and colleagues reported.

One advantage of the approach in the second part of the study, they noted, was that the majority of men who didn’t need a biopsy did not have one.

Kaplan and colleagues cautioned that, as with previous studies, the analysis could not rule out the possibility that the drug therapy induced higher grade disease, instead of just helping to detect it. But the evidence supports the latter conclusion, they argued.

“At a time when the value of PSA is being increasingly debated,” Kaplan said in a statement, “we have shown that when used in a specific way, it can be of great value in identifying men with previously undetected prostate cancer.”

The men in the study and others like them present “a challenging diagnostic dilemma,” the researchers noted as their PSA levels would suggest cancer, but their biopsies, often performed repeatedly, remain negative.