Biopsy techniques have made PSA test less predictive

The investigators found that the number of biopsies performed, the percentage of positive biopsies, and patient ages did not change significantly over time. However, there was a significant decrease in the median PSA level in patients undergoing biopsy and an increase in the median number of samples taken at the time of biopsy. Also, 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 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. Therefore, the researchers concluded that ¡°the correlation between PSA and positive biopsy rate no longer holds true in our patient population for men with a normal digital rectal exam and PSA ¡Ý2.0 ng/ml.¡±

While changes in biopsy practice patterns have improved cancer detection, these very changes ¡°have negatively influenced the predictive value of PSA in men with a normal digital rectal exam such that, using current biopsy practice patterns, PSA no longer correlates with positive biopsy rate,¡± note the authors. They cite the urgent need for new blood or urinary markers to better determine who needs a prostate biopsy, adding that aside from family history or prior atypical biopsy findings, there is little other information available to help physicians decide who needs a biopsy and who does not.

Article: "Negative Influence of Changing Biopsy Practice Patterns on the Predictive Value of Prostate-specific Antigen for Cancer Detection on Prostate Biopsy." Michael J. Schwartz, David H. Hwang, Andrew J. Hung, Jullet Han, Justin W. McClain, M. Mendel Shemtov, Alexis E. Te, R. Ernest Sosa, E. Darracott Vaughan, Jr., and Douglas S. Scherr. CANCER; Published Online: March 10, 2008 (DOI: 10.1002/cncr.23353); Print Issue Date: April 15, 2008.