#ESMO26 | HORIZON-Breast06

HER2-low mBC after ≥1 prior line of chemo for metastatic disease, or in the first-line chemo setting after prior ET (if HR+).

Trastuzumab rezetecan vs. physician’s choice of chemo

PFS: 16.4 vs 6.8 mo (HR 0.27)
ORR: 75.5% vs 41.2%
Grade ≥3 TRAEs: 84.1% vs 67.9% ILD: 2.5%.