Objective: To investigate the prognostic impact of different 2-[fluorine-18]fluoro-2-deoxy-D-glucose positron emission tomography (¹⁸F-FDG PET) parameters in patients with advanced nasopharyngeal carcinoma (NPC).
Patients and methods: A total of 196 patients with primary stage III-IVb NPC were included in the study. The following parameters derived from pretreatment ¹⁸F-FDG PET were determined: metabolic tumor volume and total lesion glycolysis (TLG) of the primary tumor, maximal standardized uptake value of the primary tumor and the neck lymph nodes. Multivariable Cox proportional hazards models were used to identify independent predictors of survival.
Results: Multivariable analysis demonstrated that TLG values greater than 330 independently predicted overall survival (P=0.0014) and disease-free survival (P=0.0005). We identified IVa-b stage and TLG values greater than 330 as independent predictors of local failure-free survival. In addition, a high maximal standardized uptake value of the neck lymph nodes (P=0.005), male sex (P=0.041), and stage IVa-b (P=0.009) independently predicted distant failure-free survival. A TLG cutoff value of 330 allowed a better stratification of overall survival and disease-free survival rates. A scoring system combining significant PET parameters and traditional prognostic factors was formulated to define distinct prognostic groups for local failure-free survival and distant failure-free survival. There was a stepwise decrease in the 5-year local (97.7, 90.4, and 47.3%, P<0.0001) and distant control rates (96.8, 88.5, 73.9, and 36.4%, P<0.0001) according to the distinct prognostic scores.
Conclusion: In patients with advanced NPC, the prognostic significance of ¹⁸F-FDG PET parameters seems to depend on the specific endpoint. The combination of PET metabolic parameters with traditional risk factors may significantly improve prognostic stratification for this group of patients.