Respiratory control and radiation therapy in breast cancer: Technical foundations, clinical evidence, and future directions.

Radiation therapy (RT) is a cornerstone in the management of breast cancer, improving locoregional, distant control, as well as survival. Nevertheless, for patients with left-sided tumours and those requiring regional nodal irradiation, the anatomical proximity of the heart and lungs to the target volumes increases the risk of radiation-associated cardiopulmonary side effects. Respiratory control is a clinically validated technique that mitigates this risk by displacing intrathoracic structures away from high-dose regions during inspiration. This narrative review provides a comprehensive, multidisciplinary synthesis of respiratory control techniques in breast cancer RT, integrating its radiobiological rationale, dosimetric performance, clinical outcomes, and technical implementation across contemporary treatment platforms including three-Dimensional Conformal Radiation Therapy (3D-CRT), Intensity-Modulated Radiation Therapy (IMRT), Volumetric Modulated Arc Therapy (VMAT), and proton therapy. Implementation barriers-particularly in low- and middle-income countries (LMICs) -are critically evaluated, and pragmatic strategies for global dissemination are proposed, including simplified protocols, shared-resource models, and capacity-building initiatives. Ultimately, respiratory control exemplifies the convergence of physiologic innovation, technological precision, and survivorship-centred care, while challenging workflow management and operational efficiency. Its incorporation into routine practice enhances the therapeutic ratio, aligns with the principles of precision oncology, and offers a scalable, cost-effective strategy to reduce global inequalities in access to high-quality breast cancer treatment.