Update and external validation of a head and neck cancer prognostic model

Background The purpose of this study was to update and external validation of a prognostic model that is able to predict the survival probability of newly diagnosed patients with head and neck cancer. Methods Our original prognostic model is based on historical data of 1371 patients with primary head and neck cancer, diagnosed and treated in the Leiden University Medical Center, between 1981 and 1999. The model contains the predictors age, sex, tumor site, TNM-classification, prior tumors, and comorbidity. We updated the model with follow-up data until January 2010. The updated model was then externally validated in 598 patients with head and neck cancer from the Siteman Cancer Center/Barnes-Jewish Hospital, St. Louis, Missouri. Results Median follow-up was 5.5 years (range, 0-25.5). Only 2.5% of patients were lost to follow-up. During follow-up 1099 patients (80.2%) passed away. Discrimination of the updated prognostic model was good, with a C-index of 0.73 after internal validation. The discrimination was slightly lower in the external validation set (C-index, 0.69). The predicted 2-year and 5-year survival rates correlated satisfactorily with some slight deviations from the perfect calibration line. Conclusions We used recent follow-up information to update the Leiden prognostic model for newly diagnosed patients with head and neck cancer. The model showed acceptably good calibration and discrimination results in internal and external validation procedures.