Abstract
BACKGROUND: 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. OBJECTIVE: To evaluate the clinical outcomes and toxicities at the end of the treatment, and up to 6 months after dose compensation for treatment interruption. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSION: 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.