Differential Prognostic Value of Metabolic Heterogeneity of Primary Tumor and Metastatic Lymph Nodes in Patients with Pharyngeal Cancer

Abstract

Background/aim: We aimed to explore the prognostic value of metabolic heterogeneity of ¹⁸F-FDG uptake in chemoradiotherapy-treated pharyngeal cancer patients.

Patients and methods: This study included 52 consecutive patients with pharyngeal cancer who underwent ¹⁸F-FDG PET/CT before definitive chemoradiotherapy. The heterogeneity factor (HF) was defined as the derivative (dV/dT) of a volume-threshold function for primary tumors and metastatic lymph nodes. The relationships between clinical parameters and HFs of primary tumors (pHF) and metastatic lymph nodes (nHF) were analyzed.

Results: The pHF (range=∓1.367 - -0.027; median=-0.152) was significantly correlated with the maximum standardized uptake value, metabolic tumor volume, and total lesion glycolysis. Induction chemotherapy response was not correlated with HF, whereas response to radiotherapy was significantly better in patients with high pHF (low heterogeneity). Consistently, the 2-year locoregional recurrence-free survival was significantly better in patients with high pHF (82.9% for pHF>-0.152 vs. 30.5% for pHF<-0.152, log-rank p=0.009). The nHF (range=-1.067 - -0.039; median=-0.160) was not correlated with response to radiotherapy and locoregional recurrences.

Conclusion: pHF, but not nHF, was a significant predictor of response to radiotherapy and locoregional recurrence in pharyngeal cancer. Thus, HF use can prevent unnecessary treatment and surgical delays.

Keywords: Metabolic heterogeneity; PET; chemoradiotherapy; pharyngeal cancer.