Modern prostate cancer biopsy scheme shows higher diagnostic yield

March 1, 2008

The modern 10- to 12-core biopsy scheme has a higher diagnostic yield than the conventional sextant biopsy scheme does, especially on second biopsy.

Key Points

The current understanding of the performance of transrectal ultrasound-guided prostate needle biopsy, both for initial biopsy and repeat biopsy, has primarily been based on sextant biopsy approaches. In these studies, cancer was likely to be found on about one-third of initial biopsies, and about one-fifth of second biopsies.

This study evaluated the diagnostic ability and other sonographic and histologic findings in a modern cohort of men being evaluated according to newer 10- and 12-core biopsy schemes. The population was a consecutive series of 455 patients undergoing 500 consecutive TRUS biopsies via a 10- to 12-core biopsy scheme from 2003 to 2005. Investigators retrospectively examined age, race, body mass index, PSA, PSA density, digital rectal exam findings (any firmness, induration, or nodule), TRUS findings, and TRUS prostate volume.

The results revealed a positive prostate cancer rate of 44% on initial biopsy (170/367), a 53% rate on second biopsy (41/77), a 23% rate on third biopsy (7/30), and a 22% rate on fourth biopsy (2/9), reported Javier Miller, MD, a urology resident working with Raj S. Pruthi, MD, and colleagues.

In a multivariate analysis of the diagnostic yields, second biopsies were found to have a greater association with prostate cancer, as compared to initial biopsies (p=.042). Initial biopsies had a greater association with prostate cancer compared to third biopsies (p=.050). The odds ratio for having a positive biopsy was 1.00 in the first biopsy, 1.92 on the second biopsy, 0.37 for the third biopsy, and 0.25 for the fourth.

Those undergoing repeat biopsies were less likely to have high-grade lesions (Gleason 4+3 or greater), more likely to have larger prostates, less likely to have an abnormal DRE, and more likely to be unilaterally positive.

"The findings suggest that with a 10- to 12-core biopsy approach, patients undergoing a second biopsy-most commonly for an ongoing rise in PSA-may actually be at a higher risk of having a positive result," Dr. Miller said. "On the other hand, those with a positive finding on the second biopsy are more likely to have a lower-grade tumor."

Addressing a 'thorny issue'

Jerome P. Richie, MD, chief of urology at Brigham and Women's Hospital, Boston, commented that the study "addresses a thorny issue," namely, the patient with a rising PSA level.

"The authors found most diagnostic yield with a second biopsy, and less with a third or fourth biopsy," he said. "My question is: When have we performed enough biopsies to be able to just follow the patient? There is no question that more biopsies do increase the chance of finding cancer. But questions about increased risks, especially infection, are becoming more important as resistance to standard antibiotics is being more frequently encountered."

Dr. Pruthi responded that he agrees that the indications for a so-called "saturation biopsy" are very limited and should not be considered a routine approach for most patients. He added that the rationale for repeat biopsies must be carefully considered.

"Two biopsies are rational, with a third and fourth added only for good reason," Dr. Pruthi said. "Such a study also highlights the need for better screening and diagnostic tests to increase the sensitivity and specificity of such studies, particularly for he detection for clinically significant tumors

Dr. Richie also considered the lack of information on PSA velocity to be a weakness of the study, since PSA levels tended to rise with each repeat biopsy in these subjects.

"The study lacked information about what happened to the rate of change in PSA levels. PSA velocity is becoming increasingly important, especially an increase in PSA of 2.0 ng/mL over a 1-year period," Dr. Richie said.