Prognostic Impact of Primary Tumor Volume in Patients With Nasopharyngeal Carcinoma Treated by Definitive Radiation Therapy

Objectives/Hypothesis: Tumor burden has been confirmed as one of the important indicators in disease control after treatment for various types of malignancies. This report aims to document the value of the primary tumor volume of nasopharyngeal carcinoma [gross tumor volume of the primary site (GTV-P)] in predicting the treatment outcome after high-dose definitive radiation therapy. Study Design: A total of 154 patients with nasopharyngeal carcinoma were prospectively treated with accelerated hyperfractionated radiotherapy alone to a total dose of 78 Gy/60 fractions/6 weeks (biological effective dose = 88.2 GY). Methods: Patients were assessed for local control, disease-free survival and distant failure free survival. The GTV-P was calculated by summation of area technique after delineation of the primary tumor contours on computed tomography images. Results: The median GTV-P was 14.5 mL for T1, 23.3 mL for T2, 35.8 mL for T3, and 50.9 mL for T4 diseases (P <.05). With a median follow-up of 61 months, the 5-year local failure-free rate, disease-free survival and distant failure-free survival rates were 89.4% versus 48.9% (P = .002), 56.6% versus 0% (P = .001), and 66.9% versus 16.5% (P = .0001), respectively, for patients whose GTV-P were <= 60 mL and > 60 mL. Multivariate analysis revealed that GTV-P is an independent prognostic factor for local control (hazard ratio = 3.568, P = .035). Therefore, the GTV-P was significantly associated With the treatment outcome after high-dose radiation delivered in accelerated hyperfractionated Schedule for nasopharyngeal cancer patients. Conclusions: Tumor volume is a reliable for supplementing the T classification of the Tumor, Node, Metastasis staging system for predicting local control after definite radiation therapy.