SAN FRANCISCO — Adjustment of threshold values of prostate-specific antigen velocity for age can substantially improve prostate cancer detection among men younger than 70 years, Dr. Judd W. Moul said at a prostate cancer symposium sponsored by the American Society of Clinical Oncology.
In a review of data from more than 11,000 men who underwent PSA testing during a 7-year period, Dr. Moul and colleagues at Duke University Medical Center in Durham, N.C., tested the hypothesis that lowering the threshold for what's considered the “normal” PSA velocity for younger age groups would help detect disease sooner than current thresholds allow.
The investigators calculated PSA velocities from patients' PSA measures over time and correlated them to prostate biopsy status. They then normalized velocity percentiles to three different age categories (40–59 years, 60–69 years, and 70 years and older).
Conventional screening protocols consider a PSA velocity increase of 0.75 ng/mL or more per year to be an indicator of increased prostate cancer risk regardless of patient age.
After adjustment of the data for patient age, the threshold PSA velocity for men aged 40–59 years was lowered to 0.25 ng/mL per year.
For men aged 60–69 years, it was lowered to 0.50 ng/mL per year. The threshold for men older than 69 remained 0.75 ng/mL, Dr. Moul said at the symposium, which was cosponsored by the Society of Urologic Oncology and the American Society for Therapeutic Radiology and Oncology.
In a comparison of the screening accuracy of the age-adjusted threshold with the traditional standard, the prostate cancer detection rate in the study cohort increased from 19% to 35% among men in the youngest category and from 25% to 57% among men in the middle age group.
“The sensitivity of the age-adjusted PSA velocity for the younger group was 0.519, compared to 0.265 for the standard,” Dr. Moul said. “For the middle age group, the sensitivity with the lower threshold was 0.398, compared to 0.306.”
Specificity values in these two groups were only slightly and nonsignificantly diminished from those associated with the conventional threshold values, he said.
Based on the findings, “it's clear that age-adjusted PSA velocity could significantly improve our ability to detect early prostate cancer,” he said.