The impact of the definition of biochemical recurrence following salvage radiotherapy on outcomes and prognostication in patients with recurrent prostate cancer after radical prostatectomy: a comparative study of three definitions

PURPOSE: The clinical management and follow-up of patients with recurrent prostate cancer after salvage radiotherapy (SRT) has not yet been established, and no standardized definition of biochemical recurrence (BCR) after SRT exists. We compared the impact of applying three different definitions of BCR following SRT on patient outcomes and prognostication. SUBJECTS: Patients who received salvage androgen-deprivation therapy before the completion of SRT were excluded. The data of 118 men who had undergone salvage radiation as monotherapy for BCR after radical prostatectomy were reviewed. In all patients, SRT comprised irradiation to the prostatic bed (70 Gy) using three-dimensional conformal radiotherapy techniques. Treatment outcomes, including BCR-free survival and prognostic factors, were analyzed and compared among three definitions: The Nara, Radiation Therapy Oncology Group (RTOG) 9601, and GETUG-AFU 16 definitions. RESULTS: The BCR rate differed significantly among the applied definitions. Multivariate analyses identified the same four independent prognostic factors, including primary Gleason pattern 4 or 5, negative resection margin, prostate-specific antigen (PSA) level before SRT 0.5 or more, and PSA doubling time before SRT <6 months, using the RTOG 9601 and GETUG-AFU 16 definitions, whereas only two of the four factors were identified using the Nara definition. Although the results obtained using the RTOG 9601 and GETUG-AFU 16 definitions were similar, the prognostic value of the four factors differed. According to the RTOG 9601 definition of BCR, a negative resection margin on prostatectomy specimens and short PSA doubling time before SRT were associated with no subsequent response in PSA level. CONCLUSIONS: The applied definition of BCR after SRT can influence the reported BCR-free rate and the potential prognostic factors. Establishment of the standardized definition is needed for the optimal management of patients with recurrent prostate cancer undergoing SRT.