Heart-Sparing Capability and Positional Reproducibility of Continuous Positive Airway Pressure in Left-Sided Breast Radiation Therapy

This study evaluated the reproducibility and practical applicability of continuous positive airway pressure (CPAP) in left breast volumetric modulated arc therapy (VMAT). The heart's interfraction position reproducibility was measured using heart-to-target distance on planning CT and daily cone beam CT scans of 20 patients, while dosimetric metrics for the heart and its substructures were compared between CPAP and free-breathing VMAT plans. Intrafraction reproducibility was assessed using 4D CT in 20 patients. Cardiac substructures were segmented using AVIEW software (Coreline Soft). The results showed an average heart-to-target distance error of 2.0 ± 2.0 mm, with CPAP significantly reducing mean heart dose and dose to the left ventricle and left anterior descending artery compared to free-breathing. The intrafraction variation of the breast target position was minimal. CPAP was successfully applied in 93% of patients, demonstrating its adequacy for heart-sparing and reproducibility in left-sided breast cancer treatment.