Stereotactic Body Radiation Therapy for Oligometastatic Prostate Cancer

Purpose: To review outcomes of patients with oligometastatic prostate cancer (PCa) treated with stereotactic body radiation therapy (SBRT) and to identify variables associated with local failure. Methods and Materials: We retrospectively reviewed records of patients treated with SBRT for oligometastatic PCa. Metastasis control (ie, control of the treated lesion, MC), biochemical progression-free survival, distant progression-free survival, and overall survival were estimated with the Kaplan-Meier method. Results: Sixty-six men with 81 metastatic PCa lesions, 50 of which were castrateresistant, were included in the analysis. Lesions were in bone (n = 74), lymph nodes (n = 6), or liver (n = 1). Stereotactic body radiation therapy was delivered in 1 fraction to 71 lesions (88%), at a median dose of 16 Gy (range, 16-24 Gy). The remaining lesions received 30 Gy in 3 fractions (n = 6) or 50 Gy in 5 fractions (n = 4). Median follow-up was 16 months (range, 3-49 months). Estimated MC at 2 years was 82%. Biochemical progression-free survival, distant progression-free survival, and overall survival were 54%, 45%, and 83%, respectively. On multivariate analysis, only the dose of SBRT was significantly associated with MC; lesions treated with 16 Gy had 58% MC, and those treated with >= 18 Gy had 95% MC at 2 years (P <=.001). At 2 years, MC for lesions treated with 18 Gy (n = 21) was 88%. No patient treated with >= 18 Gy in a single fraction or with any multifraction regimen had local failure. Six patients (9%) had grade 1 pain flare, and 2 (3%) had grade 2 pain flare. No grade 2 or greater late toxicities were reported. Conclusions: Stereotactic body radiation therapy for patients with oligometastatic prostate cancer provided optimal metastasis control and acceptable toxicity with doses >= 18 Gy. Biochemical progression-free survival was 54% at 16 months with the inclusion of SBRT in the treatment regimen. Stereotactic body radiation therapy should considered in patients with castration-refractory, oligometastatic prostate cancer who have limited options for systemic therapy. (C) 2016 Elsevier Inc. All rights reserved.