Objectives: To determine pretreatment prognostic variables that predict outcome of radiotherapy for biochemical failure after prostate cancer surgery and evaluate contemporary clinical decision tools for patient selection.
Methods: Fifty patients were identified with failure after rescue radiation was defined as a confirmed rise in PSA, distant metastases, prostate cancer death, or initiation of hormonal therapy. Univariate analysis and multivariate Cox models were constructed. Outcome was compared with decision tree and recursive partitioning predictive models.
Results: The median preradiation PSA (pre-RT PSA) was 1.2 ng/mL and the median dose of radiation was 66.6 Gy; median follow-up was 39.6 months. Overall, the estimated 3-year failure free survival was 54%, 95%CI [43,74]. Seminal vesicle involvement (SVI) (P = 0.003) and preradiation PSA Doubling Time (PSADT) <10 months (P = 0.01) were both significant predictors for treatment failure whereas pre-RT PSA was of borderline significance (P = 0.07). On multivariate analysis a pre-RT PSA of >1 and SVI were associated with hazard ratios of 6.2 and 7.3 (P = 0.01 and P = 0.004), respectively. An additional Cox model constructed for 31 patients for whom pre-RT PSADT could be calculated showed PSADT and SVI to be independent prognostic parameters. Two predictive models, a decision tree analysis, and a recursive partitioning model were moderately accurate in predicting outcome in this series, however, high-risk patients experienced less treatment failures than predicted.
Conclusions: Pre-RT PSA <1 ng/mL, longer PSADT (>10 months) and no SVI are associated with improved outcome after rescue radiation. Contemporary clinical prediction tools are imperfect predictors of outcome for rescue radiation therapy.