Clinical significance of post-chemoradiotherapy 2-[(18)F]FDG PET/CT response in locally advanced nasopharyngeal carcinoma: A real-world study.

PURPOSE: To investigate the prognostic value of post-chemoradiotherapy 2-[(18)F]FDG PET/CT in locally advanced nasopharyngeal carcinoma (LANPC) and develop an accurate prognostic model based on the 2-[(18)F]FDG PET/CT results. METHODS: 900 LANPC patients who underwent pretreatment and post-chemoradiotherapy 2-[(18)F]FDG PET/CT from May 2014 to August 2022 were included in the study. We divided the patients into two distinct cohorts for the purpose of our study: a training cohort comprising 506 individuals, included from May 2008 to April 2020, and a validation cohort consisting of 394 individuals, included from May 2020 to August 2022. PET/CT were assessed using the improved Deauville score (iDS) system. Cox regression analysis was performed to select candidate variables. A prognostic model was developed by the training cohort, and validated using the independent validation cohort. RESULTS: Age (HR, 2.262(1.488-3.439); p＜0.001), ECOG (HR, 2.450 (1.395-4.301); p = 0.002), post-treatment EBV DNA level (HR, 2.208 (1.289-3.784); p = 0.004) and iDS [iDS1-2 vs iDS3-4: HR, 3.781 (1.996-7.163); p＜0.001]; [iDS1-2 vs iDS5: HR, 11.707 (5.884-23.295); p＜0.001]were independent predictors of OS. A 4-factor prognostic model developed and subsequently validated. This innovative model demonstrated excellent discrimination (C-index: 0.862). The calibration curves revealed a close match between the predicted probabilities and the actual outcomes, and decision curve analysis (DCA) confirmed the nomogram's utility for guiding clinical decision-making. CONCLUSION: Our study validated the predictive value of the iDS system in determining outcome for LANPC. The 4-factor prognostic model, which integrates baseline patient characteristics with iDS, demonstrated good discrimination, agreement, and clinical application potential.