Tumor-specific major histocompatibility-II expression predicts pathological complete response to atezolizumab combined to chemotherapy in triple-negative breast cancer.

This study analyzed tumor-specific MHC-II (tsMHC-II) expression as a predictive biomarker in the phase III NeoTRIP trial for early-stage triple-negative breast cancer (TNBC).

Patients received neoadjuvant carboplatin and nab-paclitaxel with or without atezolizumab.

Key findings include:

• TsMHC-II positivity, defined as ≥5% tumor cell expression, was linked to a significantly higher pathological complete response (pCR) rate in patients treated with atezolizumab.
• No significant pCR improvement was observed in patients receiving chemotherapy alone.

These findings suggest tsMHC-II expression may help identify early TNBC patients more likely to benefit from neoadjuvant chemo-immunotherapy, supporting its potential role in treatment personalization.