Circumferential Stereotactic Body Radiotherapy for Spine Metastasis: The Feasibility, Toxicity and Local Control

Abstract

Circumferential spine stereotactic body radiotherapy (CsSBRT) is indicated in selected patients with circumferential vertebral bone/epidural spine metastatic disease. There is a paucity of data on the feasibility, toxicity and outcomes of CsSBRT. This study aimed to determine the feasibility, toxicities and outcomes of CsSBRT treatments.We analyzed sixty-four circumferential treatments from 2013-2019 treated with SBRT in the post-operative and intact spine metastatic setting. Radiotherapy was delivered with 1-5 fractions. We analyzed the local control, side effects and the dose-volume histogram for each treatment.In the sixty-four plans, the median follow-up was 15 months (1-63 months). All images and treatment plans were reviewed by the CNS radiation oncology and neuro-radiology. The most common regimen used was 27 Gy in 3 fractions. The 12-month cumulative incidence of local failure was 15%. In this cohort, there was eight local failures; 5 of them had recurrence in the epidural space, two had disease progression in the vertebral body and one had disease progression in the vertebral body with extension to the right lateral compartment. The planning target volume (PTV) coverage was ≥95% in 60 plans (94%). The median biologically effective dose (BED) for delivered dose, mean dose, minimum dose and D95% were 51.3 Gy, 54.13 Gy, 29.3 Gy and 51.3 Gy, respectively. The median BED max dose to spinal cord and cauda equine were 59 Gy (15-114) and 68 Gy (7.5-136). There were no grade 3 or higher early or late toxicities reported.In this retrospective analysis of patients who received CsSBRT treatments, we were able to achieve excellent local control safely with minimal toxicity. We recommend at least 2-4 mm space between the target and the spinal cord or cauda equine in order to deliver CsSBRT.K. Dibs: None. J.D. Palmer: Research Grant; Varian Medical Systems, The Kroger Company. Consultant; Huron Consulting. Speaker's Bureau; Varian Medical Systems, Depuy Synthes. Advisory Board; Novocure. Member of panel; NCCN.A. Olausson: None. E. Bourekas: None. D. Boulter: None. A.S. Ayan: None. E.R. Cochran: None. V. Yildiz: None. J.C. Grecula: None. A.L. Arnett: None. R. Raval: None. S. Beyer: None. T. Scharschmidt: None. J.B. Elder: None. A. Chakravarti: None. E. Mendel: None. D.M. Blakaj: None.