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

Abstract

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 cm3, 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 cm3, 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.

Application of Continuous Positive Airway Pressure for Thoracic Respiratory Motion Management: An Assessment in a Magnetic Resonance Imaging–Guided Radiation Therapy Environment

“…Improvement in lung dose and heart dose parameters was demonstrated in these experiences [20,24,27,28], highlighting future opportunities to quantify the dosimetric benefits of CPAP-guided MRgRT. In the case of SBRT treatment of lung tumors, the planned target volumes were decreased by 19% to 24% with administration of CPAP [20,29].…”

“…A pilot study by Goldstein et al looking at stereotactic body radiation therapy (SBRT) for lung tumors under 8-15 cm H 2 O CPAP showed a relative lung volume increase of 32% compared to standard FB [20]. Two clinical trials of women receiving left-sided breast radiotherapy highlighted that implementing CPAP led to increases of total lung volume by 35% and 60%, achieved with 8-15 cm H 2 O and 20 cm H 2 O, respectively [24,27]. One previous study of SBRT patients showed a lesser degree of 8% lung volume increase [23].…”

“…In the case of SBRT treatment of lung tumors, the planned target volumes were decreased by 19% to 24% with administration of CPAP [20,29]. Another notable takeaway in one study was that radiation therapy with CPAP did not increase treatment setup time compared with free-breathing setup, and the authors concluded CPAP may be a viable option for respiratory management in resource-limited radiation oncology centers [24]. Another clinical question that arises is the viability of CPAP in the population of patients with thoracic malignancies who often have underlying pulmonary comorbidities.…”

“…A similar analysis was performed on heart centroid displacement. Reference volumes and centroid locations for comparison were defined at the FB-0 cm H 2 O condition, similar to the standard established in other CPAP studies [20,23,24,27]. Additional comparisons were done for FB-15 cm H 2 O vs. DIBH-0 cm H 2 O as well as DIBH-0 cm H 2 O vs. DIBH-15 cm H 2 O in order to assess the relative magnitude of geometric changes associated with CPAP alone, DIBH alone, and the combination of the two.…”

“…This mechanism has also been employed sparingly in the radiation oncology setting as it is associated with increased end-expiratory volumes and decreased respiratory rate; however, it may also introduce larger tidal volumes and greater diaphragmatic movement [19]. A number of published early clinical experiences have reported deploying CPAP as a cost-effective and readily available respiratory management strategy during radiation therapy [20][21][22][23][24][25][26][27]. Here, the present work investigates the compatibility of the CPAP system with an MR-linac system while using the onboard MRI to characterize geometric changes and image quality under different CPAP-aided and DIBH conditions.…”