Practical Heart-Sparing Breast Cancer Radiotherapy Using Continuous Positive Airway Pressure (Cpap) In Resource-Limited Radiation Oncology Clinics

To report experiences of practical heart sparing breast RT using continuous positive airway pressure (CPAP) in resource limited radiation oncology clinic. Twelve patients underwent CT-simulations with both free-breathing (FB) and CPAP under the individual maximum tolerable air pressure. For each patient, left-sided breast RT plans (9 with breast only, 3 with breast and regional nodal stations) with FB and CPAP were created using 3-dimensional conformal RT (3DCRT: supine tangential RT) according to RTOG 1304. For daily RT, patients started CPAP at waiting area for 15 minutes before entering treatment room and continued it during RT. Treatment setup times among patients receiving breast RT with CPAP and others with FB were measured. All patients well tolerated CPAP with 8∼15 cmH20 of air pressure. Compared to FB, CPAP inflated the thorax and increased total lung volume by 35±16% (CPAP: 3136±751 vs. FB: 2354±657 cm3, p<0.01), caudally displaced the heart by 1.8 cm (p<0.01), and decreased heart volume within tangential RT fields by 96±5% (1.4±2.5 vs. 21±17 cm3, p=0.02) in all patients. PTV coverage was acceptable in all RT plans. CPAP lowered mean dose (Dmean) to heart by 47±22% (2.5±1.5 vs. 5.4±3.3 Gy, p<0.01); heart volume receiving ≥ 25 Gy (V25) by 82±18% (2.2±2.6 vs. 9.1±7.1%, p<0.01); Dmean to left anterior descending coronary artery by 68±8% (4.7±1.9 vs. 14.8±3.3 Gy, p<0.01). CPAP decreased radiation dose to ipsilateral lung compared to FB: 9.1±5.8 vs. 11.2±8 Gy (20% reduction, p=0.03) of Dmean; 15.7±12.5 vs. 20.5±17.5% (25% reduction, p=0.03) of V20. RT with CPAP did not increase treatment setup time compared to FB (week1: 362±63 vs. 352±77 seconds; week2∼5: 217±13 vs. 201±14 seconds, all p>0.25). Novel uses of CPAP allowed efficient and practical heart sparing breast RT without increasing infrastructural requirements in resource limited radiation oncology clinics.