Stereotactic Magnetic Resonance Guided Adaptive Radiation Therapy in One Fraction (SMART ONE): A Multicenter,...

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Stereotactic body radiation therapy (SBRT) typically uses ≤5 fractions for precise tumor radiation.
• Single-fraction SBRT for visceral tumors is limited by concerns of geographic miss due to suboptimal imaging on conventional linear accelerators (linacs).
• Magnetic resonance (MR)-guided linacs offer superior imaging, potentially enabling safer single-fraction SBRT.

Purpose of the Study:

• To evaluate the feasibility and safety of single-fraction SBRT using an MR-guided linac for various visceral tumors.
• To assess the efficacy of this treatment in terms of local control and overall survival.

Main Methods:

• A multicenter phase 2 trial involving 30 patients with primary or metastatic lesions in the lung, liver, pancreas, adrenal gland, kidney, and lymph nodes.
• Single-fraction SBRT was delivered on a 0.35 Tesla MR-linac with specific dose prescriptions for each organ.
• Primary objectives focused on feasibility and safety, with secondary outcomes including local control and overall survival.

Main Results:

• The study met its primary objectives, with 87.1% of plans completed in <90 minutes in-room time.
• One acute grade 3 adverse event was possibly related to treatment; no late grade 3-5 adverse events were observed.
• One-year local control was 96.2% and overall survival was 86.3%.

Conclusions:

• MR-guided single-fraction SBRT is a feasible, safe, and effective treatment for tumors in the lung, abdomen, and pelvis.
• This technology overcomes previous limitations associated with single-fraction SBRT for visceral tumors.
• Further research is needed to determine optimal patient selection for single- versus multifraction SBRT.