Cause-specific mortality prediction model for patients with basaloid squamous cell carcinomas of the head and neck: a competing risk analysis

Purpose: Basaloid squamous cell carcinoma (BSCC) is a rare, high-grade variant of squamous cell carcinoma (SCC). Most published studies based on population-based datasets focus on prognostic differences between SCC and BSCC. Competing risk analyses for this disease have not been performed. We used Surveillance Epidemiology and End Results (SEER) data to calculate and model the cumulative incidence of death for patients with head and neck BSCC (HNBSCC) with competing risk approaches, and built a model to predict probability of cause-specific death for these patients. Methods: We analyzed data on 1163 patients who were diagnosed with primary lip and oral cavity, oropharynx, or hypopharynx and larynx BSCC and registered in the SEER program between 2004 and 2013. We calculated crude cumulative incidence function (CIF) for mortality after diagnosis of HNBSCC. We built a Fine and Gray's proportional sub-distribution hazard model and nomogram to predict their probability of cause-specific death. We calculated concordance indexes (c-index) and plotted calibration curves to evaluate model performance. Results: Five-year cumulative incidence of cause-specific death after diagnosis of HNBSCC was 26.5% (95% CI: 23.4-29.8%); cumulative incidence of other causes of death was 11.8% (95% CI: 9.4-14.3%). Old age, large tumor size, hypopharynx and larynx sites, lymph node-positive, distant metastasis, and non-radiotherapy were significant factors for high probability of cause-specific death. The model was well calibrated. The bootstrap-corrected c-index for the model was 0.71. Conclusions: We built the first competing risk nomogram for HNBSCC. The model performance was found to be good. This individualized prognostic predictive tool will aid physicians in clinical counseling, and will assist patients in planning for their future lives.