Diagnostic Performance of Response Assessment FDG‐PET/CECT in HNSCC Treated With Definitive Radio(chemo)therapy Using NI‐RADS.

Objective: To assess the diagnostic performance of response assessment 18F‐fluorodeoxyglucose positron emission tomography/contrast‐enhanced computed tomography (FDG‐PET/CECT) following definitive radio(chemo)therapy in head and neck squamous cell carcinoma (HNSCC) using Neck Imaging Reporting and Data System (NI‐RADS). Study Design: A retrospective analysis from a prospectively maintained dataset. Setting: Tertiary‐care comprehensive cancer center in a low‐middle‐income country. Methods: Adults with newly diagnosed, biopsy‐proven, nonmetastatic HNSCC treated with definitive radio(chemo)therapy were included. Posttreatment response assessment FDG‐PET/CECT scans were retrospectively assigned NI‐RADS categories (1‐3) for the primary site, neck, and both sites combined. Locoregional recurrence occurring within 2‐years was defined as the event of interest. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy were calculated. Locoregional control stratified by NI‐RADS categories was computed with the Kaplan‐Meier method and compared using the log‐rank test. Results: Posttreatment FDG‐PET/CECT scans were available in 190 patients constituting the present study cohort. Sensitivity, specificity, PPV, NPV, and overall accuracy of the NI‐RADS template for the primary site was 73.5%, 81.4%, 46.3%, 93.4%, and 80.0%, respectively. Similar metrics for the neck were 72.7%, 87.5%, 43.2%, 96.1%, and 85.8%, respectively. Combining primary site and neck, the corresponding metrics of diagnostic accuracy were 84.4%, 69.7%, 46.3%, 93.5%, and 73.2%, respectively. At a median follow‐up of 40 months, Kaplan‐Meier estimates of 2‐year locoregional control were significantly higher for NI‐RADS category 1 (94.2%) compared to NI‐RADS category 2 (69.4%) and category 3 (20.4%), respectively (stratified log‐rank p <.0001). Conclusion: FDG‐PET/CECT using the NI‐RADS template is associated with good diagnostic performance and prognostic utility in HNSCC treated with definitive radio(chemo)therapy. [ABSTRACT FROM AUTHOR]