Direct-to-Unit Stereotactic Magnetic Resonance Imaging-Guided Adaptive Radiation Therapy for Spine Metastasis.

Abstract

This study evaluated the feasibility of a direct-to-unit stereotactic magnetic resonance imaging-guided adaptive radiation therapy (SMART) workflow for spine metastases. Ten patients with spinal metastases were prospectively enrolled. Preplans were created using diagnostic imaging, with patients proceeding directly to magnetic resonance imaging-guided adaptive treatment using online adaptation and bulk density override for dose calculation. Feasibility was defined as successful completion of the first fraction on the initial on-table attempt in ≥70% of patients. Toxicity, dosimetric outcomes, and clinical response were assessed. Delivery of first fraction on first attempt was successful 90% of the time. Of 36 total fractions, 10 required online adaptation. The median treatment time per fraction was 87 minutes. Acute toxicity was limited to grade 1 to 2 fatigue. At a median follow-up of 14 months, local control was 90% at 3 months and 67% at 6 months. Direct-to-unit SMART is a feasible and safe approach for spine stereotactic body radiation therapy, allowing treatment without conventional simulation.