Advantages of Continuous Positive Airway Pressure (CPAP) in Left-Sided Breast Radiation Therapy

Abstract

To assess the utility of continuous positive airway pressure (CPAP) as an adjunct and an alternative to deep inspiration breath hold (DIBH) in the treatment of left-sided breast cancers. Ten patients with left-sided breast cancer whose heart or lung dose constraints were not met during free breathing (FB) or DIBH simulations were included in this study. All patients were simulated using FB, DIBH, CPAP with FB, and CPAP with DIBH. Treatment plans were calculated to cover the breast/chest wall and regional nodes including the supraclavicular fossa, the axilla, and the internal mammary chain. Dose-volume histograms were calculated for heart, ipsilateral lung, and contralateral breast for each simulation. Dosimetric parameters of organs at risk were compared using the Wilcoxon signed-rank test. All simulations met current RTOG acceptable criteria for coverage of chest wall/whole breast and all regional lymph node fields. For all patients, mean heart dose was lower for simulations with CPAP, both with FB (mean 3.4 vs. 7.4, p=0.001) and with DIBH (mean 2.5 vs. 7.4, p=0.006), as compared to FB alone. For 7 out of 8 patients who had unacceptable mean heart doses in the FB and DIBH simulations, CPAP reduced mean heart dose to meet acceptable constraints (≤5Gy). CPAP significantly increased ipsilateral lung volume as compared to FB (mean 1616.8 vs. 1028.7, p=0.005). CPAP with 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 out of 10 patients did not meet ipsilateral lung V20 dose constraints (≥35% of lung receiving 20Gy) in either the free breathing or DIBH simulations, but all patients met acceptable criteria using at least one of the CPAP simulations, and 8 out of 10 met lung V20 goal constraints (≤30% of lung receiving 20Gy) in the CPAP with DIBH simulation. Contralateral breast dose was acceptable (<5% of breast receiving 4.1Gy) for all simulations, and CPAP provided no significant dose reductions. Among women with left-sided breast cancer, irradiation of the heart and lung is a major concern due to anatomical proximity of these structures to the target area. Evidence and clinical practice suggest that DIBH may reduce exposure to these non-target tissues, but may be difficult to execute in some patients and may not show acceptable benefits in others. Our results suggest that CPAP may be a viable alternative to DIBH for these patients, and that it may further reduce non-target radiation exposure when used in conjunction with DIBH.