Test-set performance of CPH models on the MSKCC and DFCI cohorts of the Director's Challenge. Each plot shows Kaplan-Meier survival curves for the predicted low-risk group (blue) and the predicted high-risk group (red). Plots show the empirical survival probability S(t) as a function of time. The hazard ratio (HR) of the high-risk versus the low-risk groups is given, along with its 95% confidence interval. Test-set performance is reported for both the (A) ISOpure cancer profiles and (B) original, unpurified profiles.