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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.
Acknowledgements
The authors are grateful to Erna Kjølsvik and Kristin Iversen for technical assistance and Ingvild Dalen for her assistance in performing and interpretation of statistical tests.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
We thank the Norwegian Cancer Society for the financial support given towards this study.
Supplementary material available online
Supplementary Figure 1 available online at http://informahealthcare.com/doi/abs/10.3109/0284186X.2014.990107
