Effect of definition of preradiotherapy prostate-specific antigen velocity on its association with prostate cancer-specific mortality and all-cause mortality.

OBJECTIVES

An 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).

METHODS

We 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.

RESULTS

The 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.

CONCLUSIONS

The 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.