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 ((3)He-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 >or=20Gy (V(20)), and the other to minimise only the functional lung volume receiving >or=20Gy (FV(20)). Dose-volume characteristics and a plan quality index related to planning target volume coverage by the 95% isodose (V(PTV95)/FV(20)) were compared between anatomical and functional plans using the Wilcoxon signed ranks test. RESULTS Compared to anatomical IMRT plans, functional planning reduced FV(20) (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 0.4Gy, 0-0.7Gy, 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 FV(20), V(20) and mean functional lung dose are possible when IMRT planning is supplemented by functional information derived from SPECT or (3)He-MRI.