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) for the CR group differed significantly (P = 0.016) from the non-CR group, while not for V and V (P > 0.05). The mean increase in ΔD 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.