Spine SABR with Simultaneous Integrated Boost Using Cyberknife : Clinical Outcomes

Spine SABR with simultaneous integrated boost using Cyberknife®: Clinical outcomes

R. Jumeau1, JB. Zerlauth2, N. Ruiz-Lopez3, V. Vallet3, EM Ozsahin1, J. Bourhis1, L. Schiappacasse1

1Department of Radiation Oncology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland

2Department of Radiology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland

3Department of Radiation Physics, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland

Introduction: Spine stereotactic ablative radiotherapy (SABR) has became a new tool in the management of metastatic patients providing higher local control rates than conventional palliative therapies. This study’s aim was to show the efficiency of spine SABR with simultaneous integrated boost (SIB) using Cyberknife®.

Materials and methods: A retrospective analysis of patients with spinal metastases treated with SABR at our institution was conducted. All patients had planning computed tomography (CT) and dedicated magnetic resonance imaging (MRI). The gross tumor volume (GTV) of each spinal metastasis was contoured on the T1- and T2-weighted MRI sagittal sequence. Each clinical target volume (CTV) was delineated according to the international spine radiosurgery consortium consensus guidelines. An additional margin of 1 mm was added to the CTV to create the planning tumor volume (PTV) and to the GTV to create the PTV boost. All patients were treated with Cyberknife®; tumor tracking was achieved using the Xsight spine tracking system. The overall survival (OS) and the local control were described using Kaplan-Meier statistics.

Results: Between October 2014 and December 2016, 32 patients with 40 spinal metastases were treated. The median follow-up was 8 months. The median prescribed dose to PTV and PTV boost were 30 Gy (range, 24 – 30) and 35 Gy (range, 27 – 35), respectively; treatments were delivered in 3 – 5 fractions. The 1-year local control rate was 97% and the 1-year OS rate was 49%. There were 2 cases (6.3%) of symptomatic vertebral fracture and no case of radiation-induced myelopathy.

Conclusion: Spine SABR with SIB is feasible and provides satisfactory local control. More work should be done to integrate SABR in the management of spine metastases even in palliative intent.