Central Nervous System
PV QA 2 - Poster Viewing Q&A 2
Purpose/Objective(s): Most of the data following spine stereotactic body radiotherapy (SBRT) are specific to thoracic and lumbar metastases. The unique anatomy and biomechanical features of the cervical spine and sacrum may impact treatment outcomes following SBRT. The purpose of this study was to report our imaging-based outcomes following SBRT specific to cervical and sacral metastases.
Materials/Methods: From our institutional prospectively maintained spine SBRT database, we retrospectively reviewed only cervical and sacral metastases. All patients were followed at 2 to 3-month intervals with a clinical visit and full spine MRI. Outcomes of interest were imaging-based local control (LC), overall survival (OS), vertebral compression fracture (VCF) and other serious adverse effects.
Results: A total of 52 patients and 93 spinal segments were identified consisting of 56 treated segments within the cervical spine and 37 within the sacrum. The median follow-up was 14.4 months and 19.5 months, respectively, and the median total dose and number of fractions was 24 Gy in 2, respectively, in both cohorts. Cumulative LC rates at 1- and 2-years were lower for the sacral cohort (86.5% and 78.7%) compared to the cervical spine cohort (94.5% and 92.7%). Lack of posterior spinal element involvement was predictive of LC in the cervical spine cohort (no local failures, p<0.0001) cohort, and absence of epidural disease (HR 0.275, 95% CI 0.076-0.989, p=0.048) predicted LC in the sacral cohort. Median OS was 16.3 months and 28.5 months in the cervical spine and sacrum cohorts, respectively. In the cervical spine group, presence vs. absence of liver and/or lung metastases was prognostic with a median survival of 10.8 months vs. not reached even after 48 months (p=0.0494), respectively. In the sacral cohort, patients with oligometastatic disease (HR 0.139, 95% CI 0.031-0.616, p=0.0094) and breast primary (HR 0.136, 95% CI 0.026-0.697, p=0.0168) had longer OS. Two cases of VCF in the sacrum, one brachial plexopathy and one lumbar-sacral plexopathy were observed.
Conclusion: Although high rates of LC were observed following SBRT to the cervical spine and sacrum, strategies specific to the sacrum may require further investigation to optimize results. Serious sequelae after SBRT to cervical spine and sacrum were rare.
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