An international pooled analysis of SBRT outcomes to oligometastatic spine and non-spine bone metastases

Purpose: There is a paucity of data on SBRT to non-spine bone (NSB) lesions compared to spine metas-tases. We report local recurrence (LR), widespread progression (WSP), and overall survival (OS) for oligo-metastatic patients treated to bone lesions with SBRT and investigate the hypothesis that outcomes are different between patients with spine and non-spine bone oligometastatic disease. Methods: Patients with oligometastatic disease (<5 cumulative extracranial metastases) treated with bone SBRT at 6 international institutions from 2007 to 2016 were reviewed. Fine and Gray competing risks and Cox regressions were used to analyze univariable and multivariable relationships between dis-ease/treatment factors and outcomes. Results: In total, 288 spine and 233 NSB lesions are reported in 356 patients. Cumulative incidence of LR across all bone lesions was 6.3%, 12.6% and 19.3% at 6 mo, 1 yr and 2 yrs. While univariable analysis sug-gested inferior LC and OS in spine patients, this did not hold true in multivariable analysis. The final regression model for LR in NSB lesions included PTV > median of 31.8 cc (HR 5.02, p = 0.014) and primary histology, with RCC and NSCLC conferring a 10.8-and 6.5-fold increased risk of LR compared to prostate histology, respectively. The spine LR model included radioresistant histology (HR 2.11, p = 0.0051), PTV Dmin (BED10) > median of 19.1 Gy (HR 0.46, p = 0.0085), and epidural disease (HR 1.99, p = 0.016). Conclusion: This large multi-institutional series reports comparably excellent response to SBRT for a bal-anced distribution of oligometastatic NSB and spine lesions. Dose escalation for large and/or radioresis-tant NSB lesions should be explored, given the typical lack of an immediately adjacent dose-limiting critical structure. (c) 2021 Elsevier B.V. All rights reserved. Radiotherapy and Oncology 164 (2021) 98-103

Automated summary

This study reviewed oligometastatic patients treated with SBRT for spine and non-spine bone lesions at six international institutions, finding no significant difference in local recurrence, widespread progression, and overall survival between the two groups. Dose escalation for large and/or radioresistant non-spine bone lesions should be considered.