THP (taxane + trastuzumab/pertuzumab) posts 43.8% pCR in stage II/IIIa HER2+ breast cancer—63.7% in ER− vs 32.4% in ER+

EA1181/CompassHER2 pCR (NCT04266249) tested neoadjuvant THP: 4 cycles of trastuzumab + pertuzumab with either weekly paclitaxel (12 weeks) or q3w docetaxel (x4), then surgery, in clinical stage II/IIIa HER2+ breast cancer (n=2,175 enrolled; n=2,141 initiated therapy; 781 HER2+/ER− and 1,394 HER2+/ER+). The overall pCR (ypT0/Tis, ypN0) rate was 43.8%, split as 63.7% in HER2+/ER− and 32.4% in HER2+/ER+; higher pCR was associated with ER−/low ER, PR−/low PR, HER2 IHC 3+, and weekly paclitaxel, while T3 predicted lower pCR only within the HER2+/ER− subset (T/N stage otherwise not strongly linked). In a genomic subset (n=569), a high HER2DX pCR score independently correlated with higher pCR after adjustment—useful signal for de-escalation-style selection, especially since commonly used multi-agent regimens with dual HER2 blockade (e.g., docetaxel/carboplatin/trastuzumab/pertuzumab) often land around ~55%–68% pCR overall in stage II–III disease, at the cost of more myelosuppression/diarrhea and regimen complexity.