Comparative Prognostic Value of Pre- and Post-Induction Chemotherapy Tumor Volumes in Locoregionally Advanced Nasopharyngeal Carcinoma

PurposeTo evaluate and compare the prognostic value of primary, nodal, and total tumor volumes before and after induction chemotherapy (IC) in patients with locoregionally advanced nasopharyngeal carcinoma (LANPC) treated with docetaxel plus cisplatin (DP regimen) IC followed by concurrent chemoradiotherapy (CCRT). Materials and MethodsWe retrospectively analyzed 164 patients with LANPC from 2016 to 2020.Primary tumor volume (GTV-P), nodal tumor volume (GTV-N), and total tumor volume (GTV-T, GTV-T = GTV-P + GTV-N) were measured before and after IC.The association between tumor volumes and overall survival (OS) and progression-free survival (PFS) was analyzed using Cox proportional hazards models, while locoregional relapse-free survival (LRRFS) and distant metastasis-free survival (DMFS) were assessed using Fine-Gray competing-risk models.Prognostic discrimination was assessed using the concordance index (C-index) and the Akaike information criterion (AIC), and risk stratification was performed using Kaplan-Meier analysis. ResultsPost-IC volumetric parameters showed superior prognostic value than pre-IC volumetric parameters.Post-IC total tumor volume (GTV-T_post) was independently associated with OS and PFS and demonstrated the best model performance.Post-IC primary tumor volume (GTV-P_post) was associated with LRRFS, whereas post-IC nodal tumor volume (GTV-N_post) was associated with DMFS.Kaplan-Meier analysis further confirmed the value of risk stratification based on post-IC tumor volumes for different survival endpoints. ConclusionPost-IC residual tumor volume showed greater prognostic value than pretreatment and derived