Prognostic value of tumor volume for patients with nasopharyngeal carcinoma treated with concurrent chemotherapy and intensity-modulated radiotherapy

Abstract

We aimed to analyze prognostic factors in patients with nasopharyngeal carcinoma (NPC) treated with concurrent chemotherapy and intensity-modulated radiotherapy (IMRT); in addition, we aimed to elucidate the value of primary gross tumor volume (GTVp) in predicting prognosis of patients. Between February 2001 and December 2008, 321 patients with NPC treated with concurrent chemotherapy and IMRT were analyzed retrospectively. GTVp was calculated from treatment planning computed tomography scans. A receiver operating characteristics (ROC) curve was used to determine the best cutoff point of GTVp. The 5-year local failure-free survival (LFFS), distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS) for NPC patients were 93.8, 80.1, 73.0, and 83.7%, respectively. Univariate and multivariate analyses indicated that GTVp had exhibited a statistically significant correlation with LFFS, DMFS, DFS, and OS (P<0.05, all), whereas T classification was not an independent prognostic factor. According to ROC curve analysis, 49and 19mL were determined as the cutoff points of GTVp for local control and distant metastasis, respectively. Based on this, 321 patients were divided into three volume subgroups. LFFS, DMFS, DFS, and OS demonstrated significant differences among patients in different volume subgroups (P<0.001, all) and were superior to T classification for predicting prognosis of NPC patients. Primary gross tumor volume is an independent prognostic factor in local control, distant metastasis, disease-free survival, and overall survival in NPC. An adjusted TNM staging system that includes GTVp as a quantitative indicator to evaluate prognosis is warranted.