New studies help clarify role of prostate cancer serum markers

PSA level remains an excellent marker for prostate cancer, and PSA velocity (PSAV) can be used to determine when to perform a biopsy, according to William J. Catalona, MD, professor of urology, Northwestern University Feinberg School of Medicine, Chicago.

Although some investigators have suggested that PSA is no longer a reliable marker for prostate cancer since the tumors detected are clinically insignificant, Dr. Catalona presented new findings here that challenge that assertion.He and colleagues analyzed data from nearly 3,000 radical prostatectomy patients who were screened from 1989 to 2004. They found a better correlation between PSA level and cancer than between PSA level and prostate size in 89% of the patients.

"While prostate size may be a confounding factor in a small percentage of patients, all of those men had prostates that were larger than 55 cc," Dr. Catalona told a media gathering here yesterday.

Determining the PSA density can help clarify whether the PSA level is due to the presence of tumor or due to benign tissue.

"A PSA density of less than 0.1 suggests that prostate size is driving the PSA level. However, a PSA density of 0.1 or higher suggests the need for a biopsy," he said.Based on new findings from a separate study, Dr. Catalona also recommended that a biopsy be performed in men whose PSA level is greater than 2.5 ng/mL when their PSAV is 0.5 ng/mL per year. In a long-term study of nearly 3,500 men who underwent prostate biopsy, 45% of those with a PSAV of 0.5 ng/mL per year were diagnosed with cancer - a cancer detection rate that is similar to the cancer detection rates for higher PSAV cutoffs.