Effect of Definition of Preradiotherapy Prostate-Specific Antigen Velocity on Its Association with Prostate Cancer-Specific Mortality and All-Cause Mortality

ObjectivesAn increasing prostate-specific antigen (PSA) velocity (PSAV) is associated with a shorter time to prostate cancer-specific mortality (PCSM) after definitive local therapy. This study examined the effect on this association when the PSAV was estimated using all PSA values (PSAV-all) instead of the PSA values within 18 months before diagnosis (PSAV-18).MethodsWe studied 358 men (median age 71.2) with clinically localized prostate cancer treated with external beam radiotherapy to a dose of 70.35 Gy from 1989 to 2002. The median follow-up was 4.0 years. The Cox and Gray’s multivariate regression analyses were used to evaluate the association between PSAV and the interval to PSA recurrence, all-cause mortality, and PCSM, adjusting for known prognostic factors.ResultsThe median PSAV-18 and PSAV-all was 1.50 ng/mL/yr (interquartile range 0.74 to 3.82) and 1.20 ng/mL/yr (interquartile range 0.69 to 3.34), respectively. Of the 358 men, 226 (63%) had only two PSA values; therefore, the estimation of their PSAV was the same, irrespective of the method used. Remarkably, despite the identical estimates for PSAV in 63% of the men in this study, after adjusting for known prognostic factors, the hazard ratios describing the significant associations with the interval to PSA recurrence, PCSM, and all-cause mortality increased and the associated P values decreased using PSAV-18 compared with PSAV-all.ConclusionsThe results of this study have shown that the PSAV estimated using the pretreatment PSA values obtained approximately 18 months before diagnosis compared with using all previous PSA values provides a stronger association with the interval to PSA recurrence, PCSM, and all-cause mortality after RT.