Prognostic Value of Lymph Node-to-Primary Tumor Ratio of PET Standardized Uptake Value for Nasopharyngeal Carcinoma: A Recursive Partitioning Risk Stratification Analysis

Abstract

To evaluate the prognostic value of the lymph node-to-primary tumor ratio (NTR) of positron emission tomography (PET) standardized uptake value (SUV) for nasopharyngeal carcinoma (NPC) patients treated with induction chemotherapy (IC). Four hundred and sixty-seven locoregionally advanced NPC patients with pretreatment 18F-fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) scans between September 2017 and November 2020 were retrospectively reviewed. All patients underwent IC plus intensity-modulated radiotherapy (IMRT). The receiver operating characteristic (ROC) analysis was used to determine the optimal cut-off value of SUV NTR. Kaplan-Meier method was used to evaluate survival rates. The recursive partitioning analysis (RPA) was performed to construct a risk stratification model. The optimal cut-off value of SUV NTR was 0.74. Multivariate analyses showed that SUV NTR and overall stage were independent predictors for distant metastasis-free survival (DMFS) and regional recurrent-free survival (RRFS). Therefore, an RPA model based on the endpoint of DMFS was generated and categorized the patients into three distinct risk groups: RPA I (low-risk: SUV NTR<7.4 and stage III), RPA II (medium-risk: SUV NTR<7.4 and stage IVa, or SUV NTR≥7.4 and stage III), and RPA III (high-risk: SUV NTR≥7.4 and stage IVa), with a 3-year DMFS of 98.9%, 93.4%, and 84.2%, respectively. ROC analysis showed that the RPA model had superior predictive efficacy than the SUV NTR or overall stage alone. SUV NTR was an independent prognosticator for distant metastasis and regional recurrence in locoregionally advanced NPC. The RPA risk stratification model base on SUV NTR provides improved DMFS and RRFS prediction over the 8th edition of the TNM staging system.