Correlations between DW-MRI and 18F-FDG PET/CT parameters in head and neck squamous cell carcinoma following definitive chemo-radiotherapy.

Background: Posttreatment diffusion–weighted magnetic resonance imaging (DW-MRI) and 18F-fluorodeoxygluocose ( 18 F-FDG) positron emission tomography (PET) with computed tomography (PET/CT) have potential prognostic value following chemo-radiotherapy (CRT) for head and neck squamous cell carcinoma (HNSCC). Correlations between these PET/CT (standardized uptake value or SUV) and DW-MRI (apparent diffusion coefficient or ADC) parameters have only been previously explored in the pretreatment setting. Aim: To evaluate stage III and IV HNSCC at 12-weeks post-CRT for the correlation between SUV max and ADC values and their interval changes from pretreatment imaging. Methods: Fifty-six patients (45 male, 11 female, mean age 59.9 + − 7.38) with stage 3 and 4 HNSCC patients underwent 12-week posttreatment DW-MRI and 18 F-FDG PET/CT studies in this prospective study. There were 41/56 patients in the cohort with human papilloma virus-related oropharyngeal cancer (HPV OPC). DW-MRI (ADC max and ADC min) and 18 F-FDG PET/CT (SUV max and SUV max ratio to liver) parameters were measured at the site of primary tumors (n = 48) and the largest lymph nodes (n = 52). Kendall's tau evaluated the correlation between DW-MRI and 18 F-FDG PET/CT parameters. Mann-Whitney test compared the post-CRT PET/CT and DW-MRI parameters between those participants with and without 2-year disease-free survival (DFS). Results: There was no correlation between DW-MRI and 18 F-FDG PET/CT parameters on 12-week posttreatment imaging (P =.455-.794; tau = −0.075-0.25) or their interval changes from pretreatment to 12-week posttreatment imaging (P =.1-.946; tau = −0.194-0.044). The primary tumor ADC mean (P =.03) and the interval change in nodal ADC min (P =.05) predicted 2-year DFS but none of the 18 F-FDG PET/CT parameters were associated with 2-year DFS. Conclusions: There is no correlation between the quantitative DWI-MRI and 18 F-FDG PET/CT parameters derived from 12-week post-CRT studies. These parameters may be independent biomarkers however in this ...