Multi-Institutional Datasets Validate the Recursive Partitioning Analysis for Overall Survival in Patients Undergoing Spine Radiosurgery for Spine Metastasis

Abstract

<h3>Purpose/Objective(s)</h3> The recently published spine radiosurgery (sSRS) recursive partitioning analysis (RPA) for overall survival (OS) separated patients into 3 distinct prognostic groups. We sought to externally validate this RPA using a multi-institutional dataset. <h3>Materials/Methods</h3> A total of 444 patients were utilized to develop the recently published sSRS RPA predictive of OS in patients with spine metastases. The RPA identified three distinct prognostic classes. RPA Class 1 was defined as KPS >70 and controlled systemic disease (n=142); RPA Class 2 was defined as KPS>70 with uncontrolled systemic disease or KPS ≤70, age ≥54 and absence of visceral metastases (n=207); RPA Class 3 was defined as KPS ≤70 and age <54 years or KPS≤70, age ≥54 years and presence of visceral metastases (n=95). We utilized data from large tertiary care centers to validate this RPA. A total of 749 patients were in the validation cohort and were divided based on their RPA Class. Kaplan-Meier method was used to estimate OS and log-rank test was used to compare OS between RPA classes. <h3>Results</h3> In the validation cohort (749 patients), the median OS was 11.0 months. One-hundred-thirteen (15.1%) patients were in RPA Class 1, 432 (57.7%) patients in RPA Class 2 and 204 (27.2%) patients in RPA Class 3. The median OS in the validation cohort based on RPA Class was 27.1 months for Class 1, 13.0 months for Class 2 and 3.5 months for Class 3. Patients in RPA Class 1 had a significantly better OS compared to those in Class 2 of the validation cohort (p<0.01). Similarly, patients in RPA Class 2 had a significantly better OS compared to those in Class 3 (p<0.01). <h3>Conclusion</h3> The external datasets from two large centers validated the spine SRS RPA successfully for RPA for OS for patients undergoing sSRS for spinal metastases. This is the first RPA for OS to have been externally validated using a large dataset. Based on this validation, upfront spine SRS is strongly supported for patients in RPA Class 1. Upfront SRS is also supported for RPA Class 2 patients. Patients in RPA Class 3 would benefit most from upfront conventional radiotherapy given their poor expected survival. Given successful external validation, this RPA helps guide physicians to identify those patients with spinal metastases who most benefit from sSRS.