Validation of Stage N3 of the Eighth Edition AJCC Staging System for Nasopharyngeal Carcinoma

The Utility of 18F-FDG-PET-CT Metabolic Parameters in Evaluating the Primary Tumor Aggressiveness and Lymph Node Metastasis of Nasopharyngeal Carcinoma

Background

Following changes in primary tumor (T) and lymph node (N) staging for nasopharyngeal carcinoma (NPC) in the Eighth Edition AJCC Cancer Staging Manual, simplification of T staging has been proposed. However, a limited range of 2-deoxy-2-[fluorine-18] fluoro-D-glucose positron emission tomography-computed tomography (18F-FDG PET-CT) metabolic parameters has been investigated. Therefore, we aimed to evaluate the primary tumor invasiveness and the lymph node metastasis (LNM) of NPC from a metabolic perspective.

Methods

A total of 435 NPC patients underwent 18F-FDG PET/CT before treatment were retrospectively examined. The primary endpoint was differences in standard uptake value (SUV), lean body mass-normalized SUV (SUL), body surface area-normalized SUV (SUS), glucose-normalized SUV (GN), metabolic tumor volume (MTV), total lesion glycolysis (TLG), and glucose-normalized total lesion glycolysis (GNTLG) of primary tumors and LNM between different T and N stages. The metabolic parameters associated with T and N staging were identified.

Results

There were significant differences between all parameters relative to the primary tumor but no significant differences in any parameter relative to the LNM and T stages. Higher mean values of TGNmax, TGNmean, TSUVpeak, and TSUSmax were associated with advanced T stages. Higher mean values of all the LNM parameters were associated with more advanced N stages. Only primary tumor metabolic tumor volume (TMTV), TSUVpeak, TSULmax, and TSUSmax showed a significant positive association with T staging, while lymph node metabolic tumor volume (LNMTV) and TSUSmax were significantly positive in N staging.

Conclusions

Our findings suggest that metabolic parameters are useful indicators of tumor invasiveness and LNM based on the Eighth Edition manual. Compared with volume-dependent parameters, TGNmax, TGNmean, TSUVpeak, and TSUSmax may be better indicators of local tumor aggressiveness. SUSmax of the primary tumor was associated with LNM. In addition to SUVmax, other metabolic parameters (eg, SULmax, SUSmax, GNmax, and GNmean) could evaluate tumor aggressiveness and LNM better.

Construction of Prognostic Nomogram in Patients with N3-Stage Nasopharyngeal Carcinoma

INTRODUCTION

The aim of the study was to retrospectively identify the metastatic influence factors and predict the prognosis and develop an individualized prognostic prediction model for patients with N3-stage nasopharyngeal carcinoma (NPC).

METHODS

The study collected 446 NPC patients with N3 stage from the Surveillance, Epidemiology, and End Results database between 2010 and 2015. The patients were classified into subgroups based on the histological types and metastatic status. Multivariable logistic, Cox regression, and Kaplan-Meier method with the log-rank test were performed. The nomogram model was created using the prognostic factors identified from Cox regression analysis. The predictive accuracy was determined based on the concordance index (c-index) and calibration curves.

RESULTS

The 5-year overall survival (OS) of the NPC patients with N3 stage was 43.9%, and the prognosis of patients without any distant metastases was largely longer than that with metastases. No difference was observed between different pathological types in the entire cohort. However, patients with non-keratinized squamous cell carcinoma had a better OS than that of the patients with keratinized squamous cell carcinoma in a nonmetastatic subgroup. Using the Cox regression analysis results, the nomogram successfully classified these patients into low- and high-risk subgroups and presented the survival difference. The c-index of the nomogram for predicting the prognosis was satisfactory.

CONCLUSION

This study identified metastatic risk factors and developed a convenient clinical tool for the prognosis of NPC patients. This tool can be used for individualized risk classification and decision-making regarding treatment of NPC patients with N3 stage.