Figure 4

Identification of best cutoffs for immunohistochemistry scores. Plot of the C-indices obtained from the trained uni- and multivariate Cox models using the dichotomized immunohistochemistry scores for MKI67 for all non-small cell lung cancer cases, adenocarcinoma, and squamous cell carcinoma. The univariate model (gray dashed line) was built based on the protein alone, the multivariate model (black dashed line) combines clinical data (age, stage, performance status) with single protein data. The C-index (y axis) was calculated for the univariate (gray dotted line) and multivariate model (black dotted line) using all possible protein cutpoints (x axis). The best cutpoint for dichotomizing the protein score was determined by the highest multivariate C-index (black bold dot). The light gray dashed line indicates the boundary line to random guessing. Kaplan–Meier analysis of overall survival stratified by MKI67 protein expression dichotomized at its best cutpoint. The corresponding plots for the other four proteins are shown in Supplementary Figure 3.