In more detail, we observed gefitinib benefits in tumours that were characterised by mutations in either TP53, SMAD4 or CDK4 amplifications (p = 0.0002, HR = 0.37 [0.21–0.63]; Supplementary Data 2; Supplementary Figs. 5c and 6a), for which the resampling-based adjustment of the conditional average treatment effect yielded padj = 0.001 with HR = 0.32 [0.14–0.86] (Supplementary Data 2; “Methods”). The gene discussed is SMAD4; the disease is neoplasm.