PSA Velocity A Better Predictor
William J. Catalona, MD, of the Northwestern Feinberg School of Medicine in Chicago, and his colleagues studied 1,222 prostate cancer patients (mean age 66 years; 95% white) who underwent radical prostatectomy and who had sufficient preoperative PSA measurements to enable calculations of PSA velocity (PSAV) and PSA doubling time (PSADT).
The study population had a median PSAV of 0.90 ng/mL per year and a median PSADT of 35 months. The PSA level was 2.5 ng/mL or less in 11% of men and 2.6-4.0, 4.1-10, and greater than 10 ng/mL in 28%, 56%, and 5% of men, respectively.The researchers studied how well commonly used thresholds from the medical literature predicted pathological tumor features and treatment outcomes. For PSAV, they used a threshold of 2 ng/mL per year; for PSADT, they used thresholds of 18 and 36 months.
Compared with a PSAV less than 2 ng/mL per year, a PSAV greater than 2 ng/mL per year predicted a reduced likelihood of organ-confined disease and an increased risk of positive surgical margins and seminal vesicle invasion. A PSADT less than 18 months did not reliably predict these adverse pathology features. Furthermore, a PSAV greater than 2 ng/mL per year was associated with biochemical progression and 10-year progression-free survival (PFS), but PSADT was not.
“For many years, PSA doubling time has been used to follow men after treatment for recurrence,” Dr. Catalona said. “In this situation, everyone starts with a PSA level of zero after surgery, and this makes subsequent elevations easier to calculate and compare, since PSADT is dependent upon the baseline PSA level. This is not the case in the pretreatment setting, where prostate cancer patients present with a wide range of PSA levels at the time of diagnosis.”
In newly diagnosed patients with clinically localized disease, PSA velocity, which is not dependent upon the baseline PSA level, is much simpler to use and correlates better with prognosis. “Thus, we believe that caution should be exercised in using PSADT in the preoperative setting or to determine the need for intervention for patients on active monitoring protocols,” Dr. Catalona said.