Simulated data: R D ( t ) and Kaplan-Meier Curves. Estimation of R D(t) associated with an hypothetical experimental treatment using artificial data simulated from a proportional hazard model (Details on the simulation are reported in the manuscript). The treatment effect is confounded by two covariates. The unadjusted Kaplan-Meier survival probabilities (- - - -) are reported together with the adjusted estimates (—–) obtained with the corrected group prognosis methods (left panel). The corresponding R D(t) estimates are reported in the right panel together with the model based constant RD estimate (with confidence interval).