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

In July 2024, a major failure in our magnetic resonance-guided linear accelerator (MR-linac) led to a 2-week treatment interruption for four patients.

To evaluate the clinical outcomes and toxicities at the end of the treatment, and up to 6 months after dose compensation for treatment interruption.

Following the guidelines of the Royal College of Radiologists, we hypo fractionated the treatments. The dose per fraction and number of fractions were recalculated using the linear-quadratic model.

Despite the treatment delay, the adapted dose had minimal impact on the oncological outcomes in the follow-up up to 6 months posttreatment. All patients demonstrated adequate tolerance to toxicity with no disease progression. Two patients achieved complete responses, while two showed partial responses.

Hypofractionation proved to be a feasible strategy for managing treatment interruptions in MR-linac adaptive radiotherapy, ensuring treatment continuity without compromising safety and efficacy. The biological approach maintained tumor control while minimizing toxicity, demonstrating its potential for broader applications in similar clinical scenarios.