Baseline sTILs as Predictors of Pathologic Response in HER2-Positive Breast Cancer
Key Clinical Takeaways
- Design/Population: This secondary analysis evaluated sTIL density in 1328 patients with clinical stage II/III HER2-positive breast cancer treated in CompassHER2 with preoperative trastuzumab plus pertuzumab and taxane-based therapy. sTILs were quantified from diagnostic biopsies and assessed continuously and categorically, including exploratory thresholds.
- Key Outcomes: Higher sTIL levels were consistently associated with increased likelihood of pCR across HER2-positive/ER-positive and HER2-positive/ER-negative subgroups. The exploratory ≥30% cutoff predicted pCR in univariable analyses across subtypes, though significance persisted in multivariable models only for HER2-positive /ER-positive disease.
- Clinical Relevance: Findings reinforce the role of the immune microenvironment in predicting response to preoperative trastuzumab plus pertuzumab and taxane-based therapy in HER2-positive breast cancer. Baseline sTILs may serve as a useful biomarker to guide preoperative therapy selection and inform trial designs aiming to optimize HER2-targeted regimens.
Sunil Badve, MD, Winship Cancer Institute, Atlanta, Georgia, discusses secondary analysis results from the CompassHER2 pCR trial which demonstrated that baseline stromal tumor-infiltrating lymphocytes (sTILs) were associated with pathologic complete response (pCR) following preoperative trastuzumab plus pertuzumab and taxane-based therapy among patients with HER2-positive breast cancer.
These results were reported at the 2025 San Antonio Breast Cancer Symposium in San Antonio, Texas.
Source:
Badve S, Zhao F, Tung N, et al. Tumor infiltrating lymphocytes (TILs) and pathologic complete response (pCR) in stage II/III HER2+ breast cancer treated with taxane, trastuzumab, and pertuzumab (THP): secondary results from the ECOG-ACRIN-1181/CompassHER2 pCR trial. Presented at SABCS 2025. December 9 - 12, 2025. San Antonio, Texas. Abstract GS1-04
