2050 - External Validation of a Spine SBRT Pain Flare Risk Stratification Model: A Foundation for aFuture Alliance Trial
Presenter(s)
K. Dibs1, B. C. Galvin2, D. Handley3, E. R. Cochran1, A. Tocaj4, A. N. Elguindy1, J. N. Hobson2, P. D. Brown5, R. Raval1, S. Zhu6, J. C. Grecula1, G. Tocaj7, E. M. Thomas8, R. Singh1, F. Fekrmandi9, A. Chakravarti1, K. W. Merrell2, D. M. Blakaj1, R. O. Kowalchuk10, and J. D. Palmer1; 1Department of Radiation Oncology, James Cancer Hospital/Wexner Medical Center, The Ohio State University, Columbus, OH, 2Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 3Center for Biostatistics, Department of Biomedical Informatics, The Ohio State University Wexner Medical Center, Columbus, OH, 4The Ohio State University, Columbus, OH, 5Department of Neurologic Surgery,, Rochester, MN, 6University of Florida, Gainesville, FL, 7Department of Radiation Oncology, The Ohio State University Wexner Medical Center, Columbus, OH, 8The Renaissance Institute of Precision Oncology & Radiosurgery, Winter Park, FL, 9Department of Radiation Medicine, Roswell Park Comprehensive Cancer Center, Buffalo, NY, 10University of Virginia / Riverside Radiosurgery Center, Newport News, VA
Purpose/Objective(s): Pain flares are a relatively common acute toxicity following spine stereotactic body radiotherapy (SBRT), with a rate of 20%. A recursive partitioning analysis (RPA)-based model has previously identified high-risk patients using tumor and spinal instability characteristics. We sought to perform an external validation of selected clinically accessible components of this model at our institution and to evaluate the incidence of pain flare in a cohort routinely treated with prophylactic steroids.
Materials/Methods:
A retrospective analysis of patients treated with spine SBRT from 2013-2019 at our institution, all of whom received prophylactic steroid tapering at the time of SBRT. Pain flares were defined as an acute post-treatment worsening of pain requiring analgesia and/or steroids. Three clinically accessible pre-treatment risk factors from the original model were assessed: renal cell carcinoma (RCC), epidural extension (Bilsky >0), and spinal instability neoplastic score (SINS >6). Patients were stratified into low-risk (no risk factors) and high-risk (>1 risk factors) groups. Association between risk factors, risk group, and pain flare were evaluated using Fisher’s exact test.Results:
A total of 173 patients were included, with a median follow-up of 19 months. Almost 21% had RCC, 43% had SINS >6, and 27% had epidural disease of bilsky more than 0. The overall incidence of pain flare was 4.6%, substantially lower than rates previously reported in SBRT cohort without uniform steroid prophylaxis. Pain flares occurred in 3% of low-risk patients and 5.7% in high-risk patients, with no statistically significant difference between groups (p=.49). Individually, RCC (p=.68), epidural extension (p=.21), and SINS >6 (p=.73) were not significantly associated with pain flare.Conclusion:
In this external validation cohort treated with prophylactic steroids, the incidence of pain flare after spine SBRT was low. Previously identified risk factors did not significantly stratify pain flare risk, suggesting that prophylactic steroids may mitigate the incidence of pain flare in the settings of spine SBRT. This model is to be adopted as the basis for a future Alliance trial, which seeks to determine whether prophylactic steroids reduce pain flare specifically in high-risk patients.