Adaptive boost target definition in high-risk head and neck cancer based on multi-imaging risk biomarkers

Publication date: Available online 21 December 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Feifei Teng, Madhava Aryal, Jae Lee, Choonik Lee, Xioajin Shen, Peter Hawkins, Michelle Mierzwa, Avraham Eisbruch, Yue Cao
Purpose¹⁸F-deoxyglucose (FDG) PET, dynamic contrast enhanced (DCE) and diffusion weighted (DW) MRI each identify unique risk factors for treatment outcomes in head-and-neck cancer (HNC). Clinical trials in HNC largely rely on a single imaging modality to define targets for boosting. This study aimed to investigate spatial correspondence of FDG uptake, perfusion and apparent diffusion coefficient (ADC) in HNC and their response to chemoradiation therapy (CRT), and to determine implication of this overlap or lack thereof for adaptive boosting.Materials and methodsForty patients with HNC enrolled in a clinical trial had FDG-PET/CT pre-CRT, and DCE and DW MRI scans pre and during CRT. Gross tumor volume (GTV) of primary tumor was contoured on post-Gd T1-weighted images. Tumor subvolumes with high FDG uptake, low blood volume (BV), and low ADC were created by using previously established thresholds. Spatial correspondences between subvolumes were analyzed using Dice coefficient and between each pair of image parameters at voxel-level were analyzed by Spearman's rank correlation coefficient.ResultsPrior to CRT, median subvolumes of high FDG, low BV and low ADC relative to primary GTV were 20%, 21% and 45%, respectively. Spearman's correlation coefficients between BV and ADC varied from -0.47 to 0.22, between BV and FDG from -0.08 to 0.59, and between ADC and FDG from -0.68 to 0.25. Dice coefficients between subvolumes of FDG and BV, FDG and ADC, and BV and ADC were 10%, 46%, and 15%, respectively. The union of the three parameters was 64% of GTV. The union of the subvolumes of BV and ADC was 56% of GTV pre-CRT, but reduced significantly by 57% after 10 fractions of RT.ConclusionHigh FDG uptake, low BV and low ADC as imaging risk biomarkers of HNC identify largely distinct tumor characteristics. A single imaging modality may not define the boosting target adequately.

Teaser

Several imaging risk biomarkers for treatment failure in head and neck cancer have been identified, largely in isolation. Understanding the spatial association between these imaging risk biomarkers is lacking, which could impact on decision making in clinical trials. This study found that high FDG uptake, low blood volume and low diffusion coefficient in head-and neck cancer identifies large distinct tumor subvolumes. Boosting target defined on a single imaging modality may not be adequate to achieve sufficient clinical benefits.


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