Spine Stereotactic Body Radiotherapy for Prostate Cancer Metastases and the Impact of Hormone Sensitivity Status on Local Control

Abstract

BACKGROUND: Stereotactic body radiotherapy (SBRT) is used to deliver ablative dose of radiation to spinal metastases. OBJECTIVE: To report the first dedicated series of spine SBRT specific to prostate cancer (PCa) metastases with outcomes reported according to hormone sensitivity status. METHODS: A prospective database was reviewed identifying patients with PCa treated with spine SBRT. This included those with hormone-sensitive PCa (HSPC) and castrateresistant PCa (CRPC). The primary end point was MRI-based local control (LC). RESULTS: A total of 183 spine segments in 93 patients were identified; 146 segments had no prior radiation and 37 had been previously radiated; 27 segments were postoperative. The median follow-up was 31 months. At the time of SBRT, 50 patients had HSPC and the remaining 43 had CRPC. The most common fractionation scheme was 24-28 Gy in 2 SBRT fractions (76%). LC rates at 1 and 2 years were 99% and 95% and 94% and 78% for the HSPC and CRPC cohorts, respectively. For patients treated with de novo SBRT, a higher risk of local failure was observed in patients with CRPC (P = .0425). The 1-year and 2-year overall survival rates were significantly longer at 98% and 95% in the HSPC cohort compared with 79% and 65% in the CRPC cohort (P = .0005). The cumulative risk of vertebral compression fracture at 2 years was 10%. CONCLUSION: Favorable LC rates were observed after spine SBRT for PCa metastases; strategies to improve long-term LC in patients with CRPC require further investigation.

A quantitative and comparative evaluation of stereotactic spine radiosurgery local control: proposing a consistent measurement methodology

“…17 Moreover, even though other works have reported pseudoprogression following SBRT to spinal metastases, 62 in this study no pseudoprogression was demonstrated. In contrast, however, 2 very recent studies by Abugharib et al 63 and Zeng et al 64 demonstrated a beneficial OS in large patient cohorts with hormone-sensitive, radiosensitive, spinal prostate metastases. Therefore, the impact of SBRT depending on tumor histology is still debatable and should be further explored in future studies.…”

Commentary: Spine Stereotactic Body Radiotherapy for Prostate Cancer Metastases and the Impact of Hormone Sensitivity Status on Local Control

“…The crude VCF risk in the study by Abugharib et al 4 was 13%, with majority occurring within 2 years. This is comparable with previously reported figures in other histologies.…”

“…This is currently being investigated in the ongoing Prostate-Cancer Treatment Using Stereotactic Radiotherapy for Oligometastases Ablation in Hormone-Sensitive Patients (PRESTO) trial. 7 Another strength of this study is that the authors 4 acknowledged that HSPC and CRPC are biologically distinct diseases with distinct treatment response. Local control was indeed superior with HSPC, either indicating increased radiation sensitivity or the synergistic effect that androgen deprivation can have on radiation response.…”

“…Abugharib et al 4 report their single-institutional retrospective series of patients with prostate cancer spinal metastases treated with SBRT over a 9-year period. The main strength of this study is that the spine SBRT technique used was refined and uniform, and the follow-up was robust with all patients undergoing radiographic and clinical follow-up every 3 months, for a median follow-up of 31 months.…”

“…Another strength of this study is that the authors 4 acknowledged that HSPC and CRPC are biologically distinct diseases with distinct treatment response. Local control was indeed superior with HSPC, either indicating increased radiation sensitivity or the synergistic effect that androgen deprivation can have on radiation response.…”