Preclinical study and phase 2 trial of neoadjuvant pyrotinib combined with chemotherapy in luminal/HER2-low breast cancer: PILHLE-001 study

The prognosis of patients with luminal/human epidermal growth factor receptor 2 (HER2)-low early breast cancer (EBC) needs to be improved. This preclinical study and phase 2 trial (ChiCTR2100047233) aims to explore the efficacy and safety of pyrotinib (a pan-HER tyrosine kinase inhibitor) plus chemotherapy in this population. Our preclinical experiments indicate a synergistic anti-tumor effect of pyrotinib plus chemotherapy in luminal/HER2-low (immunochemistry [IHC] 2+/fluorescent in situ hybridization [FISH]-negative) breast cancer models. Furthermore, 48 women with luminal/HER2-low (IHC 2+/FISH-negative) high-risk EBC are enrolled to receive neoadjuvant pyrotinib plus chemotherapy (epirubicin-cyclophosphamide followed by docetaxel). Ultimately, 26 (54.2%; 95% confidence interval [CI] 39.2%-68.6%) patients achieve the primary endpoint (residual cancer burden [RCB] 0/I). Treatment-related adverse events of grade ≥3 occur in 21 (43.8%) patients, with the most prevalent being diarrhea (10 [20.8%]). In conclusion, neoadjuvant pyrotinib plus chemotherapy has encouraging efficacy and manageable toxicity in women with luminal/HER2-low (IHC 2+/FISH-negative) high-risk EBC. This regimen warrants to be further validated.