Prognostic value of tumor burden in nasopharyngeal carcinoma

Background: The prognostic value of primary tumor volume (TV) in nasopharyngeal carcinoma (NPC) has been confirmed. However, studies of the prognosis value of tumor burden, including TV and nodal volume (NV), have been relatively infrequent. Therefore, the aim of this study was to evaluate the prognostic value of tumor burden in NPC patients treated with intensity-modulated radiotherapy. Methods: Receiver operating characteristics curves were generated to determine rational cutoff points for TV and NV. The volumes identified included 12.5, 25.0, and 50.0 mL, and 0, 12.5, and 25 mL, respectively. According to these cutoff volumes, four subgroups were established for TV as TV1-TV4, and four subgroups were established for NV as NV0-NV3. Then, the entire cohort (992 NPC patients) was divided into 16 subgroups according to these four levels of TV and NV. Based on similarities in the 5-year overall survival (OS) rates for these 16 subgroups, four patient groups were established, G1-G4. Results: The mean TV and NV values for our cohort were 39.5 +/- 30.8 mL and 16.5 +/- 17.6 mL, respectively. The 5-year distant failure-free rate, the 5-year disease-free survival rate, and the 5-year OS rate for G3 and G4 were significantly lower than those for G1 and G2. In particular, the OS curves of the four patient groups were significantly separated. A multivariate analysis identified TV >50 mL, T-stage (3-4), and N-stage (2-3) as adverse prognostic factors for OS. Conclusions: The results of this study demonstrate that tumor burden has a significant prognostic value for NPC patients treated with intensity-modulated radiotherapy. Hence, tumor burden, including TV and NV, should be incorporated into the current staging system for NPC to improve prognostic significance.