Intravoxel incoherent motion diffusion‐weighted MRI during chemoradiation therapy to characterize and monitor treatment response in human papillomavirus head and neck squamous cell carcinoma

PURPOSE: Characterize and monitor treatment response in human papillomavirus (HPV) head and neck squamous cell carcinoma (HNSCC) using intra‐treatment (intra‐TX) imaging metrics derived from intravoxel incoherent motion (IVIM) diffusion‐weighted magnetic resonance imaging (DW‐MRI). MATERIALS AND METHODS: Thirty‐four (30 HPV positive [+] and 4 HPV negative [‐]) HNSCC patients underwent a total of 136 MRI including multi‐b value DW‐MRI (pretreatment [pre‐TX] and intra‐TX weeks 1, 2, and 3) at 3.0 Tesla. All patients were treated with chemo‐radiation therapy. Monoexponential (yielding apparent diffusion coefficient [ADC]) and bi‐exponential (yielding perfusion fraction [f], diffusion [D], and pseudo‐diffusion [D*] coefficients) fits were performed on a region of interest and voxel‐by‐voxel basis, on metastatic neck nodes. Response was assessed using RECISTv1.1. The relative percentage change in D, f, and D* between the pre‐ and intra‐TX weeks were used for hierarchical clustering. A Wilcoxon rank‐sum test was performed to assess the difference in metrics within and between the complete response (CR) and non‐CR groups. RESULTS: The delta (Δ) change in volume (V)(1wk‐0wk) for the CR group differed significantly (P = 0.016) from the non‐CR group, while not for V(2wk‐0wk) and V(3wk‐0wk) (P > 0.05). The mean increase in ΔD(3wk‐0wk) for the CR group was significantly higher (P = 0.017) than the non‐CR group. ADC and D showed an increasing trend at each intra‐TX week when compared with pre‐TX in CR group (P < 0.003). Hierarchical clustering demonstrated the existence of clusters in HPV + patients. CONCLUSION: After appropriate validation in a larger population, these IVIM imaging metrics may be useful for individualized treatment in HNSCC patients. Level of Evidence: 2 J. Magn. Reson. Imaging 2017;45:1013–1023