The Role of Post-Neoadjuvant Chemotherapy Tumor Volume for Prognostication and Treatment Guidance in Loco-Regionally Advanced Nasopharyngeal Carcinoma.

The value of post-neoadjuvant chemotherapy (NACT) tumor volume for prognostication in loco-regionally advanced nasopharyngeal carcinoma (LA-NPC) is unascertained. Here, we recruited 4109 histologically proven LA-NPC (stage III-IVA) that were treated with radical chemo-intensive-modulated radiotherapy (IMRT). Post-NACT gross primary tumor (GTVp) and lymph node (GTVnd) volumes of each patient were calculated from planning computed tomography (CT). We observed similar linear association between GTVp/GTVnd and overall survival (OS); thresholds of 52 cm3 for GTVp and 12 cm3 for GTVnd were consistent for risk discretization for OS, disease-free survival (DFS), distant metastasis-free survival (DMFS), and local relapse-free survival (LRFS). Recursive partitioning analysis (RPA) modelling incorporating T-/N-categories and GTVp/GTVnd yielded four T-N-volume (TNV) risk groupings with disparate OS (p < 0.001). TNV risk stratification outperformed GTVp/GTVnd and eighth edition TNM for predicting OS (AUC 0.643 vs. 0.541-0.591; p < 0.001), DFS (0.629 vs. 0.545-0.580; p < 0.001), and DMFS (0.652 vs. 0.522-0.621; p < 0.001). NACT + concurrent chemoradiotherapy (CCRT) over NACT + IMRT was not superior for low- and low-intermediate-risk groupings (p > 0.05 for both), but superior for intermediate- and high-risk groupings in terms of OS (HR 0.68 (95% CI 0.47-0.99) for intermediate risk, 0.73 (0.55-0.97) for high risk; both p < 0.05). Overall, GTVp/GTVnd represent effective indicators for prognostication and decision-making in LA-NPC after NACT.