Construction of nomograms for nasopharyngeal carcinoma containing primary tumor size and SEER stage

BACKGROUND: At present, little attention has been paid to the impact of primary tumor size on the survival of nasopharyngeal carcinoma (NPC). We aimed to construct predictive nomograms for NPC that contain primary tumor size and Surveillance, Epidemiology, and End Results (SEER) stage as factors with the use of a national population-based registry. METHODS: A total of 1,574 NPC patients diagnosed between 2004 and 2011 were identified from the SEER database. Univariate and multivariate Cox analysis was used to screen out survival related clinical features. Then, two nomograms of 5-year overall survival (OS) and 5-year cancer-specific survival (CSS) were constructed using the significant clinical features. The concordance index (c-index) and a calibration plot were used to assess the performance of the nomograms. Furthermore, survival analyses were performed by risk score stratification. RESULTS: According to univariate and multivariate analyses, age, race, histology, primary tumor size, SEER stage, radiotherapy and chemotherapy were related to 5-year OS and CSS in NPC. All of these clinical features were included when constructing nomograms. The c-index values were 0.74 and 0.73 for the 5-year OS nomogram in the training cohort and testing cohorts, respectively. For the 5-year CSS nomogram, the c-index values were both 0.73 in the training cohort and testing cohort, respectively. The calibration plots showed that the predicted 5-year OS and CSS outcomes were in good agreement with the observed outcomes. All patients were divided into three groups according to the risk score stratification. Kaplan-Meier survival analyses showed that patients in the low-risk cohort had a greater 5-year survival benefit than patients in the medium-risk and high-risk cohorts (P<0.05). CONCLUSIONS: The predictive nomograms, which contain primary tumor size and SEER stage, can predict the rates of 5-year OS and CSS of NPC patients and can be used as an auxiliary prediction tool for future clinical practice.