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Prostate specific antigen doubling time (PSA-DT) and velocity (PSA-V) provide independent prognostic information in androgen independent prostate cancer (AIPC) patients receiving chemotherapy.

4616 Background: PSA-DT and PSA-V at AIPC have each demonstrated prognostic significance in retrospective studies. No study has compared PSA-DT and PSA-V at AIPC to determine if they are independent prognostic factors.


METHODS
PSA-DT and PSA-V were calculated in 91 AIPC patients treated with taxane chemotherapy. PSA-DT was calculated as log 2 divided by the slope of the linear regression of log PSA versus time, from the first rise above the PSA nadir on androgen deprivation therapy (ADT) until the start of the next treatment. PSA-V was calculated from the slope of the linear regression of the raw PSA values over time. PSA-DT and PSA-V were split into tertiles for analysis. The primary endpoint was overall survival (OS) from the date of AIPC. OS was analyzed using Cox proportional hazards regression.


RESULTS
In univariate analysis, shorter PSA-DT and higher PSA-V were associated with decreased OS. Also associated with decreased OS were: higher M stage at dx; PSA nadir on ADT >0.2; <12 wks to failure of ADT; presence of mets, bony mets, low Hb, high AP, and low albumin at AIPC; and type of chemotherapy. In multivariate analysis, PSA-DT ≤12 weeks (HR=3.2), PSA-V >10 ng/ml/yr (HR=2.8), PSA nadir >0.2 on ADT, low Hb, and type of taxane chemotherapy persisted as significant predictors of decreased OS (each p < 0.01). Rapid PSA-DT (≤12 wks) and high PSA-V (>10 ng/ml/yr) predicted the worst prognosis (25 mos median OS, unadjusted); slow PSA-DT (>12 wks) and low PSA-V (≤10 ng/ml/yr) the best prognosis (75 mos); and other combinations had intermediate prognoses (49 and 50 mos). Modifications of PSA-DT calculation such as nadir subtraction did not alter prognostic ability of either component.


CONCLUSIONS
PSA-V at the start of AIPC contributes prognostic information independent of PSA-DT. Future studies should investigate the relative contribution of each of these factors in predicting survival. No significant financial relationships to disclose.