Pathologic Complete Response (pCR) Rate and Predictors of Response to Taxane, Trastuzumab, and Pertuzumab in HER2‑Positive Breast Cancer: Secondary Analyses of EA1181/CompassHER2 pCR.
Nadine Tung, Fengmin Zhao, Angela DeMichele et al.
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In 30 seconds
This single-arm phase II trial evaluated neoadjuvant taxane, trastuzumab, and pertuzumab (THP) followed by surgery in patients with clinical stage II/IIIa HER2-positive breast cancer. Secondary analyses examined pathologic complete response (pCR) and associated factors. Among 2,141 patients who initiated THP, the overall pCR rate was 43.8%, with rates of 63.7% in HER2-positive/estrogen receptor-negative tumors and 32.4% in HER2-positive/estrogen receptor-positive tumors. Low hormone receptor expression, HER2 IHC 3+, weekly paclitaxel, and a high HER2DX pCR score were associated with higher pCR.
Key findings
- Overall pCR was 43.8%; rates were 63.7% in HER2+/ER- and 32.4% in HER2+/ER+ tumors.
- Higher pCR rates were associated with ER-negative or low ER expression, progesterone receptor-negative or low expression, and HER2 IHC 3+.
- Weekly paclitaxel was associated with higher pCR rates than the alternative taxane schedule.
- Among 569 patients assessed, a high HER2DX pCR score independently predicted higher pCR after adjustment for clinicopathologic variables.
Why it matters
The substantial difference in pCR by hormone receptor status highlights heterogeneity within HER2-positive breast cancer treated with THP. Associations with tumor biomarkers and the HER2DX score may help refine response estimates and risk stratification. However, pCR is a secondary endpoint here; the trial’s recurrence-free survival outcome among patients achieving pCR remains pending.
What to keep in mind
The study was single-arm, so comparisons between taxane schedules and other response-associated factors are not randomized. The primary 3-year recurrence-free survival endpoint had not yet been reported.