The application of CyberKnife stereotactic body radiotherapy in treatment of oligometastatic prostate cancer

Abstract

Objective To determine the effectiveness and safety of stereotactic body radiotherapy (SBRT)-CyberKnife for oligometastatic prostate cancer. Methods From May 2012 to February 2017, 31 patients treated by CyberKnife were retrospectively reviewed, with a median age of 67 years(range 52 to 83 years), including 50 oligometastatic and 2 primary prostate cancer patients. The median PSA level was 8.4 ng/ml(range 0 to 300.0 ng/ml) and PSA test was performed every month. PSA progression-free survival (PSA-PFS), time to initiation of androgen deprivation therapy (ADT) and local control rate (LCR) were measured as the main outcomes. Results SBRT was well tolerated and were performed as planned in all patients. No SBRT related acute or late toxicities were observed. No bone fracture was observed in patients treated by bony targeted radiotherapy. The median follow-up after SBRT was 20.7 months (range 1.2-58.3 months). The median PSA-PFS was 5.3 months (range 0-58.3 months). 1-year, 2-year, and 4-year PSA-PFS was 52.0%, 36.7% and 36.7% respectively. PSA level decrease was observed in 21 oligometastatic prostate cancer patients after SBRT, with median PSA-PFS of 12.3 months (range 1.2-58.3 months). PSA level increase was observed in 29 oligometastatic prostate cancer patients after SBRT. Six local recurrence were observed resulting in an actuarial 1-year, 2-year and 3-year LCR of 90.4%, 86.9% and 82.6%, respectively. Twelve patients treated without ADT after SBRT, with median follow-up of 8.6 months (range 2.9-58.3 months) in this subgroup. Seven patients were added ADT after SBRT, with the median time from SBRT to initiation of ADT of 13.3 months (range 3.0-24.0 months) in this subgroup. Twelve patients were treated with ADT continuously after SBRT. Conclusions CyberKnife seems to be a safe and effective treatment with tolerated adverse events and good local control for patients with oligometastatic prostate cancer. Key words: Prostate cancer; Oligometastatic; CyberKnife; Stereotactic body radiotherapy; Prostate specific antigen(PSA)