2562 - Dose-Response Relationship in Single Fraction Stereotactic Radiosurgery for Local Control of Spinal Melanoma Metastases
Presenter(s)
J. J. Bai1, S. T. Chao2, P. Pendyala2, L. Angelov3, J. H. Suh2, E. S. Murphy2, A. Magnelli2, and E. H. Balagamwala2; 1Case Western Reserve University School of Medicine, Cleveland, OH, 2Department of Radiation Oncology, Cleveland Clinic Foundation, Cleveland, OH, 3Department of Neurological Surgery, Cleveland Clinic Foundation, Cleveland, OH
Purpose/Objective(s): An optimal single fraction spine stereotactic radiosurgery (sSRS) dose for local control of spinal melanoma metastases has not been fully established. This study aims to analyze the dose-response relationship between single fraction sSRS and local control of spinal melanoma metastases.
Materials/Methods: Twenty-two patients with 54 spinal melanoma metastases that received single fraction sSRS were evaluated from an IRB-approved retrospective single-institution database. The primary endpoint was radiographic local failure (LF) after sSRS, defined as progression on imaging at the treated segment. A Fine-Gray competing risk model was used to evaluate cumulative incidence of LF and determine predictors of LF, with death as a competing risk.
Results: Fifty-four spinal melanoma metastases were treated with single fraction sSRS at doses ranging from 12 to 18 Gy. One was treated with 12 Gy, five were treated with 14 Gy, two were treated with 15 Gy, twenty were treated with 16 Gy, and twenty-six were treated with 18 Gy. With a median follow-up of six months (IQR, 3.6 – 29.2), six spinal melanoma metastases (11%; 6/54) in four patients experienced LF after sSRS. Median time to LF was 2.6 months. Of the six spinal metastases, two were treated with 14 Gy (40%; 2/5) and four were treated with 16 Gy (20%; 4/20). Two were located in the cervical spine and 4 were in the thoracic spine. There were no instances of LF in those treated with 18 Gy. The 1-year cumulative incidence of LF for lesions treated with <18 Gy was 17.8%. Higher single fraction sSRS dose was not significantly associated with increased incidence of vertebral compression fracture (p=0.74) nor pain flare (p=0.15). On multivariate analysis, lower single fraction sSRS dose (HR 0.44, 95% CI 0.28 – 0.70, p<0.001), younger age (HR 0.83, 95% CI 0.69-0.99, p=0.05), higher pain scores at consultation (HR 1.46, 95% CI 1.06 – 2.01, p=0.02) were associated with LF. Presence of epidural disease, foraminal involvement, and tumor volume were not significant factors.
Conclusion: Spinal melanoma metastases treated with higher doses of single fraction sSRS had lower rates of LF, with a 1-year cumulative incidence of LF of 17.8% in those treated with <18 Gy and no instances of LF in those treated with 18 Gy. Younger age and higher pain scores at consultation also predicted LF. Our findings suggest a dose-response relationship between single-fraction sSRS and local control in patients with spinal melanoma metastases.