Primary tumor volume calculation as a predictive factor of prognosis in nasopharyngeal carcinoma

CONCLUSIONS: Primary tumor volume (PTV) has a close relationship with survival rates of patients with nasopharyngeal carcinoma (NPC) who were treated with concurrent chemoradiotherapy (CCRT) or radiotherapy. Besides the current AJCC staging system, measurement of PTV may be needed to predict prognosis of NPC and adjust treatment strategy. OBJECTIVES: We conducted a retrospective study to elucidate the effect of PTV on treatment outcomes in patients with NPC who were treated with CCRT or radiotherapy. PATIENTS AND METHODS: A total of 66 patients with newly diagnosed NPC were enrolled in this study. Computed tomography (CT)-derived or magnetic resonance imaging (MRI)-derived PTV was calculated. The correlation between AJCC disease stage, PTV, and disease-specific survival was analyzed. Correlations between different prognostic factors were assessed using a Cox regression model. RESULTS: The median PTV for the whole series was 12.01 ml (range 1.25-166.58 ml). The median PTV was 3.45 ml in T1 disease, 7.96 ml in T2 disease, 17.95 ml in T3 disease, and 64.73 ml in T4 disease. Disease stage and T stage carried no prognostic significance (p=0.25 and p =0.30, respectively). Four categories of PTV (<12.5 ml, 12.5-25 ml, 25-50 ml and >50 ml) had prognostic significance (p=0.02). Survival analysis demonstrated a significant difference in overall survival with larger tumor volume (risk ratio 5.447; p=0.044).