A, Median overall survival was 21.6 months (95% CI, 18.1-28.5 months) for patients who received tucatinib plus trastuzumab and capecitabine (TUC + Tras + Cape) and 12.5 months (95% CI, 11.2-16.9 months) for those who received placebo plus trastuzumab and capecitabine (Pbo + Tras + Cape). B, Median progression-free survival was 9.9 months (95% CI, 8.4-11.7 months) for patients who received TUC + Tras + Cape and 4.2 months (95% CI, 3.6-5.7 months) for those who received Pbo + Tras + Cape. CNS indicates central nervous system.