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

Abstract

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 ( 18 F-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 18 F-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 TGN max , TGN mean , TSUV peak , and TSUS max 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), TSUV peak , TSUL max , and TSUS max showed a significant positive association with T staging, while lymph node metabolic tumor volume (LNMTV) and TSUS max 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, TGN max , TGN mean , TSUV peak , and TSUS max may be better indicators of local tumor aggressiveness. SUS max of the primary tumor was associated with LNM. In addition to SUV max , other metabolic parameters (eg, SUL max , SUS max , GN max , and GN mean ) could evaluate tumor aggressiveness and LNM better.