Single-institution Experience for Interrupted Radiotherapy in Magnetic Resonance Guided Accelerator

Area of Science:

• Radiation Oncology
• Medical Physics

Background:

• A magnetic resonance-guided linear accelerator (MR-linac) experienced a major failure in July 2024.
• This incident caused a 2-week treatment interruption for four patients undergoing radiotherapy.

Purpose of the Study:

• To evaluate clinical outcomes and toxicities after a treatment interruption.
• To assess the impact of dose compensation strategies up to 6 months post-treatment.

Main Methods:

• Hypofractionated treatments were administered following Royal College of Radiologists guidelines.
• Dose per fraction and number of fractions were recalculated using the linear-quadratic model for dose compensation.

Main Results:

• Despite the interruption, adapted dosing showed minimal impact on oncological outcomes up to 6 months post-treatment.
• All patients tolerated toxicity adequately with no disease progression observed.
• Two patients achieved complete response, and two achieved partial response.

Conclusions:

• Hypofractionation is a feasible strategy for managing MR-linac treatment interruptions in adaptive radiotherapy.
• This approach ensures treatment continuity, safety, and efficacy.
• The biological dose adaptation strategy maintained tumor control and minimized toxicity.