Efficacy and Optimal Pressure of Continuous Positive Airway Pressure in Intensity-Modulated Radiotherapy for Locally Advanced Lung Cancer

SIMPLE SUMMARY: Radiation pneumonitis is a major late complication in radiotherapy (RT) for lung cancer. Respiratory gating radiotherapy and deep inspiration breath hold are representative techniques to protect the normal lung by managing the movement of the tumor. However, these are highly patient-dependent techniques. Continuous positive airway pressure (CPAP) is used as an alternative, but it is unclear how much pressure will be effective. We aimed to determine the optimal pressure of CPAP for RT through changes in the dosimetric parameters and lung volume according to pressure. The air pressure was raised in five steps of 4, 7, 10, 14, and 17 cmH(2)O and a CT scan was performed at the baseline and at each pressure step, accompanied by contouring and RT planning. CPAP linearly increased lung volume and decreased the dosimetric parameter in the pressure range 7 to 13 cmH(2)O (p < 0.01). Above 13 cmH(2)O, V5 of the heart also showed a significant decrease (p < 0.01). ABSTRACT: We aimed to determine the optimal pressure of continuous positive airway pressure (CPAP) for radiotherapy (RT) through changes in the dosimetric parameters and lung volume according to pressure. Patients with locally advanced lung cancer, who underwent CPAP during computed tomography (CT) simulation, were included. The air pressure was raised in five steps of 4, 7, 10, 14, and 17 cmH(2)O and a CT scan was performed at the baseline and at each pressure step, accompanied by contouring and RT planning. Paired t- and Wilcoxon signed rank tests were used to compare the volumetric and dosimetric parameters according to pressure and interpressure. A total of 29 patients were selected, and 158 CT datasets were obtained. The lung volume increased significantly at all pressures (p < 0.01). The Dmean of the lung decreased significantly from 7 cmH(2)O (p < 0.01), the V5, V10, V15, and V20 of the lung decreased significantly from 7 cmH(2)O with increasing pressure, and the Dmean and V5 of the heart decreased significantly from 14 cmH(2)O with increasing pressure. The V50 showed no significant differences at any pressure. We recommend the use of at least 7 cmH(2)O with 14 cmH(2)O as the optimal pressure to achieve the effect of heart preservation.