Proposed prognostic scoring system evaluating risk factors for biochemical recurrence of prostate cancer after salvage radiation therapy

Objective To update a previously proposed prognostic scoring system that predicts risk of biochemical recurrence (BCR) after salvage radiation therapy (SRT) for recurrent prostate cancer when using additional patients and a PSA value of 0.2 ng/mL and rising as the definition of BCR. Patients and Methods We included 577 patients who received SRT for a rising PSA after radical prostatectomy in this retrospective cohort study. Clinical, pathological, and SRT characteristics were evaluated for association with BCR using relative risks (RRs) from multivariable Cox regression models. Results With a median follow-up of 5.5 years after SRT, 354 patients (61%) experienced BCR. At 5 years after SRT, 40% of patients were free of BCR. Independent associations with BCR were identified for the PSA level before SRT (RR [doubling]: 1.25, P < 0.001), pathological tumour stage (RR [T3a vs T2] 1.21, P = 0.19; RR [T3b/T4 vs T2] 2.09, P < 0.001; overall P < 0.001), Gleason score (RR [7 vs < 7] 1.63, P < 0.001; RR [8-10 vs < 7] 2.28, P < 0.001; overall P < 0.001), and surgical margin status (RR [positive vs negative] 0.71, P = 0.003). We combined these four variables to create a prognostic scoring system that predicted BCR risk with a c-index of 0.66. Scores ranged from 0 to 7, and 5-year freedom from BCR for different levels of the score was as follows: Score = 0-1: 66%, Score = 2: 46%, Score = 3: 28%, Score = 4: 19%, and Score = 5-7: 15%. Conclusion We developed a scoring system that provides an estimation of the risk of BCR after SRT. These findings will be useful for patients and physicians in decision making for radiation therapy in the salvage setting.