Continuous positive airway pressure with deep inspiration breath hold in left-sided breast radiation therapy

A dosimetric study to evaluate the use of continuous positive airway pressure (CPAP), with free-breathing (CPAP-FB) or with deep inspiration breath hold (DIBH-CPAP) an adjunct and alternative to DIBH to reduce heart and lung dose in the radiation therapy (RT) of breast cancer planned for left side RT with regional nodes and internal mammary. A retrospective analysis of 10 left-sided breast cancer patients whose heart or lung dose constraints were not met after RT planning based on FB or DIBH simulations and were referred for CPAP-based planning. All patients were simulated using FB, DIBH, CPAP-FB, and CPAP-DIBH. Treatment plans were calculated to cover the breast/chest wall and regional nodes using tangential field-in-field technique (FiF). Dose-volume parameters for heart, ipsilateral lung, and contralateral breast were compared using the Wilcoxon signed-rank test. For all RT plans, mean heart dose (Gy) was lower for treatment plans with CPAP: CPAP-FB (mean 3.4 vs 7.4, p = 0.001) and CPAP-DIBH (mean 2.5 vs 7.4, p = 0.006) compared to FB alone. CPAP-DIBH also significantly reduced MHD as compared to DIBH alone (mean 2.5 vs 4.3 Gy, p = 0.013). CPAP-DIBH significantly reduced mean lung dose as compared to both FB (mean 14.4 vs 20.1, p = 0.005) and DIBH alone (mean 14.4 vs 17.4, p = 0.007). Eight of 10 patients did not meet ipsilateral lung V20Gy dose constraints (≥35% of lung receiving 20 Gy) in either the free breathing or DIBH plans, whereas 8 out of 10 met lung V20Gy goal constraints (≤30% of lung receiving 20 Gy) in the CPAP-DIBH plans. Based on the outcomes of our study, CPAP could be a strategy for reducing lung and heart dose, both in patients not able to execute DIBH and as an adjunct in those not deriving sufficient dose reduction from DIBH alone.