ATLANTA—PSA levels between 4 and 10 ng/mL have a significant positive predictive value (PPV) for finding prostate cancer in men undergoing extended biopsies, according to results of a study presented at the 101st Annual Meeting of the American Urological Association (abstract 468). For men with a normal digital rectal exam (DRE), PSA levels between 4 and 10 ng/mL are associated with a 25% to 68% likelihood of finding some cancer on biopsy, with the PPV varying based on age and PSA level, the study found.
"There are very few diagnostic tests for cancer that perform with a PPV of between 25% and 50%," study investigator Joseph C. Presti, Jr., MD, said at a press conference.
While test performance can be assessed by different criteria, Dr. Presti suggested that PPV is the most clinically relevant measure. "A PPV tells the patient what he wants to know: ‘If my test is positive, what's the chance I have cancer?'" said Dr. Presti, professor of urology, Stanford University School of Medicine.
In their study, Dr. Presti and his colleagues examined outcomes in 999 asymptomatic men age 50 to 79 with PSA levels between 4 and 10 ng/mL who had undergone their first prostate biopsy, a 12-core extended biopsy scheme, at Stanford University. The men in the study were stratified by age, DRE result, and PSA level.
For men in their 50s with a normal DRE, the PPV of PSA for finding any cancer ranged from 36% for a PSA of 4.0-5.9 ng/mL to 45% for a PSA of 8.0-9.9 ng/mL. The PPV for finding a high-grade cancer (Gleason score 7 or higher) was 14% to 23%. Numbers were comparable for men age 60 to 69. PSA was more predictive for men age 70 to 79, for whom the PPV was 50% to 68% for detecting any cancer and 26% to 53% for detecting high-grade cancer.
As would be expected, PSA was more predictive for men with abnormal DREs, for whom the PPV was 50% to 60% for having any cancer and 25% to 45% for having high-grade cancer. However, Dr. Presti said, PSA is less important for men with an abnormal DRE, as a biopsy is always warranted in that situation.
