Abstract
PURPOSE: To describe organs at risk (OARs)-sparing breast cancer (BC) radiotherapy (RT) for patients with ipsilateral (Ipsi-diaphragm) paralysis using continuously positive airway pressure (CPAP) and supine tangential RT-field. MATERIAL AND METHOD: Breast RT plans with free-breathing (FB) for a patient with right-sided BC (patient1) and another patient with left-sided BC (patient2) showed an elevated Ipsi-diaphragm and displaced portions of liver (patient1) and the heart and intestine (patient2) into supine tangential RT-field. Although both patients denied cardiopulmonary symptoms, their elevated diaphragm, liver, intestine and the heart were unchanged with deep-inspiration breath hold (DIBH) while contralateral diaphragm moved caudally suggesting clinical diagnosis of Ipsi-diaphragm paralysis. Subsequently, patients underwent CT-sim under CPAP to create supine tangential breast RT plan. RESULT: Compared with FB, CPAP inflated lungs and moved both patients paralyzed diaphragm, liver, heart, and intestine caudally and displaced these OARs away from breast RT-field. The liver volume within right supine tangential RT-fields in patient1 was 163 cc with FB versus 12 cc with CPAP (93 % reduction). The heart and intestine were completely outside the left supine tangential RT-field with CPAP in patient2. For dosimetric comparison, supine tangential RT-fields for breast-only RT were used with prescription of 40 Gy in 15 fractions on each patients' CT-sim with FB and CPAP, respectively. Compared with FB, CPAP reduced liver volume receiving ≥ 30 Gy by 94 % (FB:140 vs CPAP:8 cc) in patient1 and mean dose to the heart by 67 % (FB:2.7 vs CPAP:0.9 Gy) and left anterior descending artery by 84 % (FB:25 vs CPAP:3.9 Gy), maximum dose to the intestine by 90 % (FB:40.6 vs CPAP:4.4 Gy). CONCLUSION: BC patients with Ipsi-diaphragm paralysis, CPAP provided an effective and practical technique for OARs-sparing breast RT.