Prognostic nomogram to predict the distant metastasis after intensity-modulated radiation therapy for patients with nasopharyngeal carcinoma

Distant metastasis-free survival (DMFS) significantly differs among individuals with nasopharyngeal carcinoma (NPC). This analysis was carried out to find prognostic risk factors of DMFS and create a nomogram to predict DMFS for NPC patients who received Intensity-Modulated Radiation Therapy (IMRT). During March 2008 to January 2010, 437 patients with confirmed NPC from First Affiliated Hospital of Guangxi Medical University were recruited into this study. We developed a nomogram for predicting DMFS according to Cox regression analysis. Nomogram performance was assessed by concordance index (C-index), bootstrap validation method, and operating characteristics curves (ROC), respectively. Four independent prognostic factors for distant metastasis were identified, including age, chemotherapy, N-stage and residual tumor. C-index of the nomogram for prediction of DMFS was 0.807 (95% confidence interval, 0.726 to 0.738), which was confirmed using bootstrap validation, indicating satisfactory predictive accuracy. The calibration curves also showed adequate agreement in predicting the 3 and 5-year DMFS. The 3 and 5-year area under the curve (AUC) of ROC for nomogram and TMN stage were 0.828 and 0.612, 0.809, and 0.571, respectively. Classifying risk subgroups based on optimal cut-off value contributes to the effective discrimination of distant metastasis. The nomogram developed for this study is useful for oncologists to accurately predict DMFS and facilitates individualized treatment for patients with NPC.