Five-year outcomes of stereotactic body radiation therapy (SBRT) for prostate cancer: the largest experience in China

OBJECTIVE: To evaluate the efficacy and safety of SBRT for localized prostate cancer (PCa) with CyberKnife in China. Moreover, it is the largest-to-date pilot study to report 5-year outcomes of SBRT for localized PCa from China. METHODS: In this retrospective study, 133 PCa patients in our center were treated by SBRT with CyberKnife (Accuray Inc., Sunnyvale, USA) from October 2012 to July 2019. Follow-up was performed every 3 months for efficacy and toxicity evaluation. Biochemical progression-free survival (bPFS) and toxicities were assessed using the Phoenix definition and the Common Terminology Criteria for Adverse Events (CTCAE) v.5.0, respectively. Factors predictive of bPFS were identified with COX regression analysis. RESULTS: 133 patients (10 low-, 21 favorable intermediate-, 31 unfavorable intermediate-, 45 high-, and 26 very high risk cases on the basis of NCCN risk classification) with a median age of 76 years (range 54–87 years) received SBRT. The median dose was 36.25 Gy (range 34–37.5 Gy) in 5 fractions. Median follow-up time was 57.7 months (3.5–97.2 months). The overall 5-year bPFS rate was 83.6% for all patients. The 5-year bPFS rate of patients with low-, favorable intermediate-, unfavorable intermediate-, high-, and very high risk PCa was 87.5%, 95.2%, 90.5%, 86.3%, and 61.6%, respectively. Urinary symptoms were all alleviated after SBRT. All patients tolerated SBRT with 1 (0.8%) patient reporting grade-3 acute and 1 (0.8%) patient reporting grade-3 late genitourinary (GU) toxicity, respectively. There were no grade 4 toxicities. Gleason score (P < 0.001, HR = 7.483, 95%CI: 2.686–20.846) was the independent predictor of bPFS rate after multivariate analysis. CONCLUSION: SBRT is an efficient and safe treatment modality for localized PCa with high 5-year bPFS rates and acceptable toxicities.