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

PURPOSE: This study evaluated the feasibility of a direct-to-unit stereotactic magnetic resonance imaging-guided adaptive radiation therapy (SMART) workflow for spine metastases.

METHODS AND MATERIALS: 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.

RESULTS

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.

CONCLUSIONS

Direct-to-unit SMART is a feasible and safe approach for spine stereotactic body radiation therapy, allowing treatment without conventional simulation.