Progressive site-directed therapy for castration-resistant prostate cancer: localization of the progressive site as a prognostic factor

Abstract Purpose Locoregional therapy for oligometastatic prostate cancer has generated great interest. However, the benefit for castration-resistant prostate cancer (CRPC) has not been fully demonstrated. Our objective was to evaluate the treatment outcome of progressive site-directed therapy (PSDT) for oligoprogressive (OP-CRPC). Methods and Materials This study cohort consisted of 101 CRPC patients who underwent whole-body diffusion-weighted MRI (WB-DWI) between 2014 and 2018 when a new line of anticancer therapy was being considered. For OP-CRPC, PSDT with radiotherapy and unchanged continuation of systemic therapy were recommended. Results Thirty-eight patients were diagnosed with OP-CRPC and 23 (61%) underwent PSDT at a median prostate-specific antigen (PSA) level of 7.8 ng/mL. The regional radiotherapy targets were the prostate/pelvic lymph nodes (n = 7), bone (n = 15), or both (n = 1). A decrease in PSA levels of at least 50% in response to PSDT (50%PSA-decline) was observed in 16 cases (70%); the median time to PSA progression was 8.7 months. Intrapelvic localization of progressive lesions was a significant predictor of time to PSA progression (hazard ratio, 6.6; P = 0.007) as well as volumes of abnormal signal intensity on WB-DWI (hazard ratio, 0.5; P = 0.045). A 50%PSA-decline was achieved in 16 (89%) of the 18 intrapelvic OP-CRPC patients and in none of the 5 non-intra-pelvic OP-CRPC patients (P Conclusions PSDT can be an effective treatment option for OP-CRPC. Progressive site localization was an important factor in good PSA response.