ERBB2 and breast cancer: DESTINY-Breast 03 was a phase 3 trial comparing T-DXd and the ADC trastuzumab emtansine (T-DM1) for 524 taxane/trastuzumab pretreated patients with metastatic HER2-positive breast cancer, at a median follow up of 28 months, the PFS was 28.8 months vs 6.8 months favoring T-DXd (HR 0.33, 95% CI 0.26-0.43, p < 0.000001), there was also an improvement in OS (41 vs 34 months, HR 0.64, 95% CI 0.47-0.87, p0037) [29,35].