title: Correlation between target volume and electron transport effects affecting heterogeneity corrections in stereotactic body radiotherapy for lung cancer.
abstract: Recently, stereotactic body radiotherapy (SBRT) for lung cancer is conducted with heterogeneity-corrected treatment plans, as the correction greatly affects the dose delivery to the lung tumor. In this study, the correlation between the planning target volume (PTV) and the dose delivery is investigated by separation of the heterogeneity correction effects into photon attenuation and electron transport. Under Institutional Review Board exemption status, 74 patients with lung cancer who were treated with SBRT were retrospectively evaluated. All treatment plans were generated using an anisotropic analytical algorithm (AAA) of an Eclipse (Varian Medical Systems, Palo Alto, CA) treatment planning system. Two additional plans were created using the same treatment parameters (monitor units, beam angles and energy): a plan with no heterogeneity correction (NC), and a plan calculated with a pencil beam convolution algorithm (PBC). Compared with NC, AAA and PBC isocenter doses were on average 13.4% and 21.8% higher, respectively. The differences in the isocenter dose and the dose coverage for 95% of the PTV (D95%) between PBC and AAA were correlated logarithmically (ρ = 0.78 and ρ = 0.46, respectively) with PTV. Although D95% calculated with AAA was in general 2.9% larger than that for NC, patients with a small PTV showed a negative ΔD95% for AAA due to the significant effect of electron transport. The PTV volume shows logarithmic correlation with the effects of the lateral electron transport. These findings indicate that the dosimetric metrics and prescription, especially in clinical trials, should be clearly evaluated in the context of target volume characteristics and with proper heterogeneity correction.
authors: Department of Radiation Oncology, Indiana University School of Medicine, 535 Barnhill Drive RT 041, Indianapolis, IN 46202, USA yakino@iupui.edu.
authors: Yuichi
authors: Y
authors: Akino
authors: Department of Radiation Oncology, Indiana University School of Medicine, 535 Barnhill Drive RT 041, Indianapolis, IN 46202, USA.
authors: Indra J
authors: IJ
authors: Das
authors: Department of Radiation Oncology, Indiana University School of Medicine, 535 Barnhill Drive RT 041, Indianapolis, IN 46202, USA.
authors: Higinia R
authors: HR
authors: Cardenes
authors: Department of Radiation Oncology, Indiana University School of Medicine, 535 Barnhill Drive RT 041, Indianapolis, IN 46202, USA.
authors: Colleen M
authors: CM
authors: Desrosiers
mesh_terms: D000465:Algorithms; D004579:Electron Transport; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery*; D011874:Radiometry / Q000706:statistics & numerical data; D016634:Radiosurgery / Q000706:statistics & numerical data*; D012189:Retrospective Studies
keywords: heterogeneity corrections; lung cancer; radiation dosimetry; stereotactic body radiotherapy