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

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• Spine metastases present a significant clinical challenge requiring effective radiation therapy.
• Conventional simulation for spine stereotactic body radiation therapy (SBRT) can be time-consuming and introduce logistical complexities.

Purpose of the Study:

• To evaluate the feasibility of a direct-to-unit stereotactic magnetic resonance imaging-guided adaptive radiation therapy (SMART) workflow for patients with spine metastases.
• To assess the safety, dosimetric outcomes, and clinical response of this novel workflow.

Main Methods:

• Prospective enrollment of ten patients with spinal metastases.
• Direct-to-unit treatment using MRI-guidance, online adaptation, and bulk density override for dose calculation.
• Feasibility defined as successful completion of the first fraction on the initial on-table attempt in ≥70% of patients.

Main Results:

• Successful delivery of the first fraction on the first attempt in 90% of patients.
• Online adaptation was required for 10 out of 36 total fractions.
• Median treatment time per fraction was 87 minutes.
• Limited acute toxicity (grade 1-2 fatigue) was observed.
• At a median follow-up of 14 months, local control rates were 90% at 3 months and 67% at 6 months.

Conclusions:

• Direct-to-unit SMART is a feasible and safe approach for spine SBRT.
• This workflow streamlines treatment delivery by eliminating the need for conventional simulation.
• The technique demonstrates promising local control for spine metastases.