ERBB2 and breast cancer: Similarly, in the RxPONDER study which included 4984 eligible patients with node-positive HR + HER2‒ early-stage BC and RS results of 0–25 who were randomized to CT plus ET vs ET alone, 481 events were reported (across treatment arms) including 116 non-breast second malignancies, 56 local/regional recurrences, and 35 contralateral BC6.