Spine Radiosurgery for the Treatment of Patients with Contiguous Multilevel Spine Metastases

Introduction: Spine radiosurgery (SRS) has been traditionally employed for 1-2 contiguous vertebral levels due to concerns regarding setup accuracy, efficacy, and radiation toxicity, especially to the spinal cord and esophagus. The NRG Oncology/RTOG0631 randomized clinical trial comparing conventional fractionated radiotherapy (RT) to SRS restricted enrollment to 1-2 contiguous spine levels. This study specifically evaluated patients with metastases spanning ≥ 3 contiguous levels treated with SRS to determine the safety and efficacy of its use for this expanded indication.

Methods: Analysis of a prospectively collected database of 49 patients with 55 metastases spanning ≥ 3 contiguous vertebral levels treated with SRS at a single institution (2002-2023) was performed. Patient characteristics were recorded, including treatment history, dosimetry, local control (LC), pain outcomes, and overall survival. The median single-fraction prescription dose was 15 Gy (range: 8-18); multifractionated treatment utilized prescription doses of 18-30 Gy in 2-5 fractions.

Results: Median follow-up was 7 months (range: 1-103) with 7 instances (13%) of local progression after 6 months (range: 5-45). Six-month, 1-year, and 2-year LC rates were 97%, 85%, and 79%, respectively. No specific prognostic factors were associated with LC. Pain was reported to improve or remain stable for 49 lesions (89%). Only ten minor adverse radiation events were identified (18%): pain flare (5%), dermatitis (4%), and de novo or progressive vertebral fractures (9%). No instances of esophageal toxicity or myelopathy were observed.

Conclusion : This study of SRS for multilevel spine metastasis is one of the largest to investigate outcomes in this challenging clinical scenario. Spine SRS conferred high rates of local control with minimal toxicity for patients even with multilevel disease which was previously considered a relative contraindication. Spine SRS may be considered for patients with extensive metastatic disease instead of conventional fractionated RT, thus affording higher rates of local control and possibly the prevention of future surgical intervention.