Continuous positive airway pressure in breast cancer radiotherapy: Protocol of a prospective clinical trial

Abstract Background Radiotherapy (RT) improves survival and local control after breast-conserving surgery (BCS) for breast cancer (BC) but can also cause toxicity. Preliminary studies suggest that continuous positive airway pressure (CPAP) reduces organ-at-risk (OAR) doses in left-sided BC RT. This prospective trial evaluates whether CPAP reduces OAR doses in a larger patient cohort, including both left and right-sided cases, and identifies which patients benefit most. Furthermore, this study investigates the feasibility of CPAP in BC RT, by evaluating patient comfort, radiation time, accuracy and reproducibility. Methods BC patients requiring BCS and RT are prospectively enrolled —left-sided cases with or without regional nodal irradiation (RNI), or right-sided cases requiring RNI. Each patient undergoes an additional CT simulation with CPAP—free breathing (FB) for right-sided cases and deep inspiration breath hold (DIBH) for left-sided cases. Left-sided patients unable to perform DIBH or ≥ 70 years old are evaluated in FB. Two RT plans (with and without CPAP) are compared. If CPAP reduces mean heart or contralateral breast dose by ≥0.5 Gy, or mean lung dose by ≥1 Gy, treatment is delivered with CPAP. Patient comfort is assessed through surveys. Sample size calculations indicated that 53 patients are required to detect a ≥0.5 Gy reduction in mean heart dose. Discussion This is the first large, prospective study to evaluate CPAP in both left- and right-sided BC patients, aiming to demonstrate OAR dose reductions and assess feasibility. The final aim is to provide patient-selection models and guidelines for clinical implementation. Trial registration The study is registered on Clinicaltrials.gov (NCT07373782).