For years, prostate specific antigen, or PSA, levels have been used to correlate prostate biopsy results in detecting prostate cancer. But a new study in the journal Cancer suggests that PSA is less effective in prostate cancer screening because of improved biopsy techniques.

The clinical data on effectiveness of PSA levels was gathered primarily in the 1990s. Today, prostate biopsies are performed differently, more often, and more frequently for each individual patient. Researchers from the New York Presbyterian Hospital of the Weill Medical College of Cornell University in New York City retrospectively analyzed all of their institution's prostate biopsies performed between 1993 and 2005. Of these, 1,607  fit the inclusion criteria for a study to determine whether changes in prostate biopsy practices might have change PSA test predictive value.

The investigators found that the number of biopsies performed, the percentage of positive biopsies, and patient ages did not change significantly over time. However, the median PSA level in patients undergoing biopsy decreased significantly and the median number of samples taken at the time of biopsy increased. In addition, fewer biopsies were performed for the indication of a suspicious digital rectal exam and there was an increase in the percentage of patients undergoing biopsy for PSA readings between 2.5 and 3.99 ng/ml. According to the American Cancer Society, the PSA level usually goes above 4 ng/ml when prostate cancer develops, but about 15% of men with a PSA below 4 ng/ml will have prostate cancer on biopsy.

The study also showed that the positive biopsy rate in men with PSA levels in the 2.0 to 3.99 ng/ml range equaled or surpassed that for patients with higher PSA readings. The researchers concluded that this called into question the usefulness of PSA for readings at this level and said there is urgent need for new blood or urinary markers to better determine who needs a prostate biopsy. The report appears in the March 10, 2008, online issue and April 15, 2008, print issue of Cancer. Lead author is Michael J. Schwartz.