Respiratory motion management for external radiotherapy: 2025 update

Respiratory motion significantly impacts the precision of radiotherapy for thoracic and abdominal tumours. This article updates a prior review on respiratory management in radiotherapy, focusing on emerging technologies and clinical implementations. Respiratory-induced tumour motion, ranging from 1 to 3cm during free breathing, introduces uncertainties in imaging, target delineation, and dose delivery. To mitigate these, various respiratory motion management strategies have been developed, encompassing techniques such as deep inspiration breath-hold, internal target volume (ITV), mid-position approaches, gating, and real-time tracking. Recent advancements, including intelligent four-dimensional computed tomography, magnetic resonance imaging-guided linear accelerators, and surface-guided radiotherapy, enhance imaging quality and treatment precision. Dosimetric studies show these technologies reduce radiation exposure to healthy tissues, particularly in complex scenarios like left-sided breast cancer or locally advanced non-small cell lung cancer. Despite clear dosimetric benefits, clinical outcome comparisons among respiratory motion management techniques remain limited, necessitating further investigation. Successful respiratory motion management integration into clinical workflows requires interdisciplinary collaboration, patient-specific strategy selection, and systematic quality assurance. Emerging methods, such as mechanically assisted non-invasive ventilation and advanced magnetic resonance imaging-based gating, further refine motion management. Quality assurance protocols, including end-to-end tests using dynamic phantoms, ensure the reproducibility and accuracy of respiratory motion management strategies. This review highlights the importance of adapting respiratory motion management techniques to patient-specific needs and evolving technologies. By addressing respiratory motion, radiotherapy can achieve improved tumour targeting and reduced toxicity, paving the way for more effective and patient-centred cancer treatments.