The Value of Tumor Diameter in Predicting Prognosis of Nasopharyngeal Carcinoma Treated with Intensity-Modulated Radiotherapy

Objective. The tumor, node, and metastasis staging system of nasopharyngeal carcinoma (NPC) has limitations in predicting prognosis. The aim of this study was to explore the prognostic value of tumor diameter for patients with NPC who were treated with intensity-modulated radiotherapy. Study Design. Case series with chart review. Setting. Affiliated Cancer Hospital of Guangxi Medical University. Subjects and Methods. The cases of 137 NPC patients treated with intensity-modulated radiotherapy were retrospectively reviewed. Tumor diameter was measured on pretreatment magnetic resonance images. Receiver operating characteristic curve was used to find the optimal cutoff value of tumor diameter and to examine the predictive ability of tumor diameter combined with T classification. Results. The mean tumor diameter increased with the advancing of T classification. The 5-year cumulative survival rates for patients with a tumor diameter <43 mm vs >= 43 mm were 88.4% vs 61.8% (P < .001), respectively. In multivariate analysis, tumor diameter was an independent prognostic factor for 5-year cumulative survival. For patients with T3 + T4, the 5-year cumulative survival rate was higher in the group with a tumor diameter <43 mm vs >= 43 mm (86.2% vs 60.2%, P = .022). The area under the receiver operating characteristic curve was 70.3% for tumor diameter combined with T classification, superior to T classification (area under the curve = 66.2%). Conclusion. Tumor diameter may be related to the extent of tumor invasion and can provide important information on prognosis. The incorporation of 43 mm as a cutoff value of tumor diameter may help to refine the predictive power of the current staging system for NPC.