Nomogram for distant metastasis-free survival in patients with locoregionally advanced nasopharyngeal carcinoma

Objective To develop and validate a nomogram to predict distant metastasis-free survival of patients with locoregionally advanced nasopharyngeal carcinoma. Methods We collected the total clinical data of 820 nasopharyngeal carcinoma (NPC) patients, of whom 482 formed the training cohort from one hospital and 328 made up the validation cohort from another hospital. By analyzing the prognosis of all patients after intensity-modulated radiotherapy by univariate and multivariate Cox regression models, a nomogram related to DMFS was created in the training cohort. The discriminatory and calibration power of the nomogram was successively assessed in the training and validation cohorts by the C-index and calibration curve. The predictive ability for 3-year DMFS was compared between the nomogram and TNM stage using ROC curves. Patients were divided into different risk groups based on scores calculated from the nomogram. Results Age, lymph node gross tumor volume (GTVnd), and gross tumor volume of the nasopharynx (GTVnx) were the factors included in the nomogram. The C-index of the nomogram was 0.721 in the training cohort and 0.750 in the validation cohort. The calibration curves were satisfactory. Patients in the high-risk group were more likely to develop metastases. Conclusion A nomogram incorporating age, GTVnd, and GTVnx showed good performance for predicting DMFS in patients with locoregionally advanced NPC.