Prognostic Model of Death and Distant Metastasis for Nasopharyngeal Carcinoma Patients Receiving 3DCRT/IMRT in Nonendemic Area of China

Abstract

Few studies were conducted to explore the prognostic factors for nonendemic nasopharyngeal carcinoma (NPC) in the era of 3-dimensional conformal radiation therapy (3DCRT)/intensity-modulated radiation therapy (IMRT). The aim of this study was to evaluate the potential prognostic factors for nonendemic NPC.Between January 2004 and December 2011, a total of 393 nonendemic NPC patients receiving 3DCRT/IMRT were reviewed according to the inclusion and exclusion criteria. The prognostic factors we analyzed included age, T stage, N stage, lymph node diameter, primary tumor volume, WHO histology types, and cranial nerve related symptoms. All patients were staged according to the 7th edition of the American Joint Committee on Cancer (AJCC) system. The factors found to be associated with the endpoints by univariate analyses were then entered into multivariate Cox proportional hazards regression analysis.The median follow-up time was 61.4 months (range: 4-130 months). The 5-year local recurrent-free survival (LRFS), nodal relapse-free survival (NRFS), distant metastasis free survival (DMFS), and disease-specific survival (DSS) for all patients were 89.3%, 96.4%, 73.5%, and 74.3%, respectively. Multivariate analysis indicated that N stage (N2-3), WHO pathologic type II, and primary tumor volume (>23 mL) were 3 independent prognostic factors for DSS and DMFS. According to the number of prognostic factors, patients were divided into 3 risk groups: low-risk group (patients without any risk factors); intermediate-risk group (patients with only 1 risk factor); and high-risk group (patients with more than 2 risk factors). The 5-year DSS for low, intermediate, and high-risk groups were 91.5%, 75.2%, and 49.3%, respectively (P < 0.001). The 5-year DMFS for low, intermediate, and high-risk groups were 89.4%, 77.9%, and 49.4%, respectively (P < 0.001).Advanced N stage (N2-3), larger tumor volume (>23 mL), and histological WHO type II are independently prognostic factors for nonendemic NPC patients in China.

FIGURE 1

Microscopy morphology of nasopharyngeal nonkeratinizing carcinoma was shown here. (A) Differentiated subtype (40×) showing cellular stratification (black arrow), pavementing, and well-defined cell distinct (white arrow). (B) Undifferentiated subtype (40×) showing syncytial sheets of large tumor cell without distinct border, vesicular nuclei, and large central nucleoli.

FIGURE 2

Survival curves of OS and DMFS according to the prognostic model in all patients. DMFS =distant metastasis free survival, OS = overall survival.

FIGURE 3

Survival curves of OS and DMFS according to the prognostic model in stage III-IVB patients. DMFS =distant metastasis free survival, OS = overall survival.