Salvage radiotherapy (SR) in patients (pts) with prostate cancer (PC) and rising prostate specific antigen (PSA) after radical prostatectomy (RP): Results from a single-center study

Abstract

14556 Background: In pts with PC and biochemical relapse after RP SR is well established. However, the significance of pre-radiotherapeutic variables for guidance of treatment decisions is less clear. We analyzed prognostic factors in a large cohort of pts treated with SR after RP. Methods: 163 pts with PC and persisting PSA-levels (n = 60) or PSA-elevation following undetectable PSA-levels (n = 103) after RP received three-dimensional conformal radiotherapy (RT). None received androgen depriving therapy between prostatectomy and start of RT. We evaluated the impact of age, stage, surgical margin status (SMS), Gleason score and PSA-kinetics by survival and regression analysis. Biochemical progression (BP) was defined as PSA-increases at 3 consecutive time points after the post RT nadir. To detect thresholds for significant prognostic variables, we calculated receiver operating characteristic (ROC) curves. Results: Medians for pre-RT variables were: 11.97 ng/ml for pre-prostatectomy PSA (Pre-OP PSA), 5.4 months for PSA doubling time (PSADT) and 0.339 ng/ml for pre-radiotherapy PSA (Pre-RT PSA). Probability for a projected 4-year PFS was 50% (median follow-up: 33.5 months). Logistic regression revealed a significant impact on the probability of BP for Pre-OP PSA (p = 0.036), PSADT (p = 0.024) and tumor-stage (p = 0.043), whereas Pre-RT PSA and SMS had a significant impact on achievement of undetectable post-RT PSA (p = 0.009 and p = 0.028 respectively). Analysis of ROC-curves for Pre-OP PSA, Pre-RT PSA, PSADT revealed an area under the curve not exceeding 0.704 for any of these parameters. Conclusions: By analyzing ROC-curves we could not detect clear thresholds for PSA kinetic variables. In accordance with recently published data we found similar independent significant variables predicting a therapeutic success. However, we observed a lower median Pre-RT PSA and a higher probability of PFS in our patient cohort. This suggests, that early radiotherapeutic intervention improves PFS. No significant financial relationships to disclose.