Practical Heart Sparing Breast Cancer Radiation Therapy Using Continuous Positive Airway Pressure (CPAP) in Resource-Limited Radiation Oncology Clinics.

Purpose: The purpose of this study was to report experiences of practical heart sparing breast radiation therapy (RT) using continuous positive airway pressure (CPAP) in resource-limited radiation oncology clinics. Patients and Methods: Twelve patients underwent computed tomography-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 (supine tangential or wide tangential RT fields) according to RTOG 1304. For daily RT, patients started CPAP in the patients waiting area for 15 minutes before entering the treatment room and continued CPAP during RT. Treatment setup times between breast RT with and without CPAP were compared. Results: All patients tolerated CPAP well with 8 to 15 cm H2O of air pressure. Compared with FB, CPAP inflated the thorax and increased total lung volume by 35 +/- 16% (CPAP: 3136 +/- 751 vs. FB: 2354 +/- 657 cm(3), P<0.01); caudally displaced the heart by 1.8 cm (P<0.01); and decreased heart volume within tangential RT fields on computed tomography-simulation scans by 96 +/- 4% (1.4 +/- 2.5 vs. 21 +/- 17 cm(3), P=0.02) in all patients. Planning target volume coverage was acceptable in all RT plans. CPAP lowered mean dose (D-mean) 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); D-mean 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 with FB: 9.1 +/- 5.8 versus 11.2 +/- 8 Gy (20% reduction, P=0.03) of D-mean; 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 with FB (week 1: 362 +/- 63 vs. 352 +/- 77 s; week 2 to 5: 217 +/- 13 vs. 201 +/- 14 s, all P>0.25). Conclusion: Novel use of CPAP allowed efficient and practical heart sparing breast RT without increasing infrastructural requirements in resource-limited radiation oncology clinics.