PSA Velocity Threshold is Too High
Researchers recommend lowering it to 0.3-0.5 ng/mL per year when PSA level is below 4 ng/mL.
ORLANDO—New findings presented here suggest clinicians should use a lower PSA velocity (PSAV) to recommend prostate biopsies in men who have PSA levels less than 4 ng/mL.
"PSA velocity is a useful predictor of prostate cancer risk in men with total PSA levels less than 4," lead researcher Stacy Loeb, MD, of the Georgetown University School of Medicine in Washington, D.C., told attendees of the third annual Prostate Cancer Symposium here. "However, the traditional threshold of 0.75 ng/mL per year is too high for these men, and we recommend instead using a threshold in the range of 0.3 to 0.5 ng/mL per year, which is actually a stronger predictor of prostate cancer than age, race, or family history."
In its 2006 guidelines, the National Comprehensive Cancer Network recommends a PSA velocity cutoff of 0.5 ng/mL per year to recommend a biopsy.
The findings by Dr. Loeb and her colleagues are based on a study of 501 men who had a PSA level of 4 ng/mL or lower, were diagnosed with prostate cancer, and had sufficient data available for PSAV calculation. Prostate cancer was diagnosed in 223 men (2%) who had a PSAV less than 0.4 ng/mL per year compared with 278 men (13%) who had a PSAV greater than 0.4 ng/mL/year.
A PSAV greater than 0.4 ng/mL/year was a significant independent predictor of prostate cancer. A threshold of 0.3 to 0.5 ng/mL per year had an area under the curve of about 0.69 compared with 0.65 for the 0.75 ng/mL per year threshold.
The findings of Dr. Loeb's group echo those of another study presented at the conference in which researchers from Northern Ireland concluded that lower PSAV cutoffs in younger men (0.2-0.4 ng/mL per year) provide a better balance of sensitivity and specificity compared with a cutoff of 0.75 ng/mL per year.
In other symposium news, researchers found that percent free PSA is the most informative predictor of prostate cancer risk in men with a total PSA value of 2.5 ng/mL or less. Jochen Walz, MD, of the Centre Hospitalier de l'Université de Montréal, and his team studied 574 men (mean age, 62.5 years) who had a total PSA level of 2.5 ng/mL or less. Of the 574 men, 131 (22.8%) had prostate cancer detected on initial biopsy.
Percent free PSA was 68.3% accurate in predicting prostate cancer at initial biopsy, which was more accurate than PSA density and transition zone density (63.1% and 65.3%, respectively).