Fulvestrant or Capecitabine Combined With Pyrotinib in HR+/HER2+ Metastatic Breast Cancer

Hormone receptor (HR) positive and human epidermal growth factor receptor-2 (HER-2) positive breast cancer has the characteristics of mild biological behavior and slow progression. Currently, capecitabine combined with pyrotinib is the standard protocol for this kind of advanced breast cancer after trastuzumab failure, and the median progression free survival (PFS) is 11.0 months. The incidence of grade 3 hand-foot-syndrome was 16.4%, the incidence of grade 3 diarrhea was 30.6%, and the incidence of grade 3 myelosuppression was 6%. Therefore, the search for efficient and low toxicity alternatives has become a research hotspot. Our previous basic studies have shown that ER inhibitor fulvestrant and HER2 inhibitor pyrotinib have synergistic effect in inhibiting the proliferation of HR + / HER2 + breast cancer cells. At the same time, the preliminary analysis of our prospective, phase II, single arm study of "Fulvestrant combined with Pyrotinib in the treatment of HR + / HER2 + advanced breast cancer" shows that the efficacy is close to that of capecitabine combined with pyrotinib (median progression free survival is more than 13 months), and the adverse events are significantly improved compared with capecitabine combined with pyrotinib (grade 3 hand-foot-syndrome). This project has been supported by the "Sun-yat sun clinical research and cultivation project" of Sun-Yat Sen Memorial Hospital, Sun-Yat Sen University. Therefore, it is necessary to further carry out a head-to-head phase III randomized controlled clinical trial to study the efficacy and safety of fulvestrant combined with pyrotinib in the treatment of HR + / HER2 + advanced breast cancer, with a non-inferiority cut-off value of HR = 1.30. Combined with the analysis of biomarkers, to find the molecular indicators to predict the benefit of pyrotinib combined with endocrine therapy, so as to provide theoretical basis for guiding precise treatment.