Benefits of Continuous Positive Airway Pressure (CPAP) in Radiotherapy: A Prospective Trial

Abstract

Non-invasive ventilation is a novel approach to manage motion and improve geometry in radiotherapy. In a previous pilot cohort, we demonstrated that Continuous Positive Airway Pressure (CPAP) significantly increases lung volume, reduces tumor motion, distancing the heart from the chest wall, and reduces radiation exposure to normal tissues. Here we report the dosimetric benefit and safety results of expanded cohort of this prospective clinical trial of CPAP in radiotherapy. This IRB approved clinical trial was conducted between December 2013 and 2016, NCT02324530. Inclusion criteria included adult patients with primary or secondary lung tumors, left sided breast cancer and liver metastases referred for RT. Following informed consent and brief training, subjects underwent 4D simulation twice: without CPAP (free-breathing (FB)) and with CPAP. PTV was created by 0.5 cm expansion of the ITV. Treatment was planned using a programming interface AAA algorithm on both simulations. Volumetric and dosimetric parameters were compared with Student’s test (categorical variables) and linear regression (continuous variables). Toxicity was reported according to CTCAE V4. 49 patients were recruited. 6 patients withdrew consent prior to simulation, 3 subjects withdrew due to CPAP mask discomfort. Complete comparative volumetric data with and without CPAP was available for 40 patients, and dosimetric comparison was available for 24 patients for whom treatment plans were prepared on both simulations. Mean age 62 (range 31-86), median ECOG: 0 (range 0-3), 28 patients were treated with SBRT and 12 with standard fractionation. 20 patients treated for single lesions and 20 patients multiple lesions. Ultimately, 27 patients were treated with CPAP and 13 with FB. Median lung volume increased to 3909 cc vs 2915 cc, relative increase of 37% (p< 0.001). Increased lung volume with CPAP was independent of age, BMI, gender, COPD, smoking status and heart disease. Tumor motion was decreased as reflected in a median reduction of PTV by 19% (p<0.001). Mean lung dose by reduced by 15%, bilateral lung V20 by 20%, lung V5 by 11%, heart V5 by 16% (p<0.01 for all). All patients treated with CPAP tolerated the intervention without complications. Grade 2 pneumonitis was reported in 4/40 patients (cough), grade 3/40 pneumonitis in 1/40 patient, rib fractures in 3/40 patients, and grade 2 esophagitis in 4/40 patients. In this prospective clinical trial, the largest to date, use of CPAP was associated with significant geometric, volumetric, and dosimetric benefits compared to free breathing. CPAP was safe and well tolerated by most patients, and reduces radiation exposure to normal organs.