Incidence and Prognostic Factors of Painful Vertebral Compression Fracture Caused by Spine Stereotactic Body Radiotherapy

Abstract

Most studies of vertebral compression fracture (VCF) caused by stereotactic body radiotherapy (SBRT) do not mention the symptoms. We aimed herein to determine the rate and prognostic factors of painful VCF caused by SBRT for spinal metastasis. Between August 2013 and December 2021, spinal segments with VCF were retrospectively identified in patients treated with spine SBRT. Iatrogenic VCFs, excluding pathological fractures, were classified into a modified group and graded using CTCAE v5.0 as grade 1 (painless), grade 2 (mildly painful), or grade 3 (intensely painful, requiring hospitalization or surgery). The primary endpoint was the rate of painful VCF (grades 2-3). Moreover, various factors specific to the patient, tumor, and treatment were evaluated to determine their value in predicting the rate of painful VCF. In total, 934 spinal segments in 387 patients were analyzed. The median follow-up after SBRT was 14 (range: 0-107) months. Sixty iatrogenic fractures (6.4%) comprising 31 de novo fractures and 29 existing VCF progressions were identified. The patients' median age was 68 (range: 38-79) years, and 31 (52%) spinal segments had a history of radiotherapy. Grade 1, 2, and 3 VCFs were confirmed in 41, four, and 15 segments, respectively. The rate of grade 3 VCF was 2.0% (19 / 934) of the spinal segments treated with SBRT. Eight (0.9%) VCFs required surgery for stabilization or decompression of spinal canal stenosis. None of the 17 VCFs treated with posterior decompression and fixation before SBRT developed into a painful VCF. On univariate analysis, the painful VCF rate was significantly higher in patients with no posterolateral tumor involvement than in those with bilateral or unilateral involvement (56.3% vs 22.7%; p = 0.026). Other spinal instability neoplastic score (SINS) components (Location, Pain, Bone lesion, Alignment, Vertebral body collapse), SINS (Stable/ Potentially unstable vs Unstable), age, number of spinal levels, radiation history, existing VCF, and interval between SBRT and VCF showed no significant correlation with painful VCF. Although VCF is a known adverse effect of spine SBRT, 68% of the cases examined were painless (grade 1). Intensely painful VCFs (grade 3) were confirmed in only 1.6% of all the treated spinal segments. The absence of posterolateral tumor involvement was significantly associated with painful VCF.