Lymph node-to-primary tumor standardized uptake value ratio on PET predicts distant metastasis in nasopharyngeal carcinoma

Objectives: To investigate the prognostic value of the relative maximum standardized uptake value (SUV) ratio between neck lymph node and primary tumor (NTR) measured by pretreatment F-18-FDG PET in patients with nasopharyngeal carcinoma (NPC). Materials and methods: We retrospectively reviewed patients with non-disseminated NPC who underwent PET scans before radical intensity-modulated radiotherapy (IMRT). Receiver operating characteristic analysis was performed to identify the optimal cut-off value for NTR. The prognostic value of NTR for distant metastasis-free survival (DMFS) was evaluated using Kaplan-Meier method for survival analyses and Cox regression for multivariable analysis. Results: Among the 437 eligible patients, the median follow-up time was 62.9 (range, 2.1-113.0) months. Patients with high NTR (NTR > 0.9181) experienced significantly worse DMFS (5-year 80.5% vs. 91.6%, P < 0.001). In the subgroup analysis, we found that patients with high NTR had significantly lower DMFS in T1-2 category (5-year 86.1% vs. 98.1%, P = 0.002), T3-4 category (5-year 71.5% vs. 86.2%, P = 0.010), N2-3 category (5-year 75.3% vs. 86.2%, P = 0.048), and stage IVA-B (5-year 69.8% vs. 85.4%, P = 0.012). Multivariable analysis showed that NTR was an independent prognostic factor for DMFS (HR 2.20, 95% CI 1.20-4.03, P = 0.011). Conclusion: Pretreatment NTR is an easily accessible but potential prognosticator for DMFS in NPC patients treated by IMRT, which may help in providing more personalized treatment or designing future clinical trials.