Pulmonary function tests-an easy selection method for respiratory-gated radiotherapy in patients with left-sided breast cancer

Abstract

Purpose: The purpose of this study was to establish a feasible and convenient method for selection of the subset of patients with left-sided breast cancer for whom respiratory-gated radiotherapy (RT) would be necessary to meet the national recommendation regarding radiation dose to the heart. Material and methods: The volume of heart receiving a dose equal to or higher than 25 Gy (V25Gy), the mean heart dose (Dmean) and total lung volume (TLV-CT) were obtained from treatment plans based on computer tomography (CT) series recorded during free breathing (FB), and the correlation between dose to the heart and TLV-CT was studied. Second, the correlation between TLV-CT and TLV defined from three pulmonary function tests (PFTs); spirometry, gas diffusion and plethysmograhy, was evaluated. Results: Dose to the heart (V25Gy and Dmean) decreased with increasing TLV-CT. Pearson's correlation coefficient (r) for TLV-CT versus V25Gy and Dmean was equal (r = -0.809, p < 0.01) for patients planned for tangential breast RT only, and r = -0.853 and -0.861 (p < 0.01) for patients planned for loco-regional RT. Regression analysis showed good correlation between TLV-CT and TLV calculated from pulmonary function tests (R2 ≥ 0.717, p < 0.01). Conclusion: TLV defined by routine pulmonary function tests can be used to identify the subset of left-sided breast cancer patients who require respiratory-gated RT.