Functional image-based radiotherapy planning for non-small cell lung cancer: A simulation study

Background and purpose: To investigate the incorporation of data from single-photon emission computed tomography (SPECT) or hyperpolarized helium-3 magnetic resonance imaging (He-3-MRI) into intensity-modulated radiotherapy (IMRT) planning for non-small cell lung cancer (NSCLC). Material and methods: Seven scenarios were simulated that represent cases of NSCLC with significant functional lung defects. Two independent IMRT plans were produced for each scenario; one to minimise total lung volume receiving >= 20 Gy (V-20), and the other to minimise only the functional lung volume receiving >= 20 Gy (FV20). Dose-volume characteristics and a plan quality index related to planning target volume coverage by the 95% isodose (V-PTV95/FV20) were compared between anatomical and functional plans using the Wilcoxon signed ranks test. Results: Compared to anatomical IMRT plans, functional planning reduced FV20 (median 2.7%, range 0.6-3.5%, p = 0.02), and total lung V-20 (median 1.5%, 0.5-2.7%, p = 0.02), with a small reduction in mean functional lung dose (median 0.4 Gy, 0-0.7 Gy, p = 0.03). There were no significant differences in target volume coverage or organ-at-risk doses. Plan quality index was improved for functional plans (median increase 1.4, range 0-11.8, p = 0.02). Conclusions: Statistically significant reductions in FV20, V-20 and mean functional lung dose are possible when IMRT planning is supplemented by functional information derived from SPECT or He-3-MRI. (C) 2009 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 93 (2009) 32-36