Objective  To evaluate the efficacy and safety of pyrotinib in managing patients with HER-2 negative advanced breast cancer, with HER-2 mutation.

  Methods  A retrospective analysis was performed using the clinical data of 13 patients with HER-2 negative advanced breast cancer, with HER-2 mutation, admitted to the Huan Xing Cancer Hospital, Chaoyang District, Beijing, from January 2018 to June 2019. All patients were managed with pyrotinib monotherapy against HER-2. The therapeutic efficacy and adverse events of the patients were comprehensively evaluated.

  Results  Among the 13 patients, three were excluded from the study because of intolerant adverse events before the first tumor response evaluation. Among the ten remaining patients, one patient achieved a complete response (CR), three patients achieved partial response (PR), three patients achieved a best response of stable disease (SD), and three patients experienced progressive disease (PD). The objective response (CR+PR) rate was 40.0% (4/10), the clinical benefit (CR+PR+SD≥6.0 months) rate was 60% (6/10), and the disease control (CR+PR+SD) rate was 70% (7/10). The longest progression-free survival (PFS) time was 15.5 months, and the median PFS was 4.9 months (95% CI: 3.8-6.0). The main toxicity related to pyrotinib was diarrhea, accounting for 84.6% (11/13). Adverse events above grade 3 experienced by the patients included diarrhea (2/13, 15.4%), nausea (1/13, 7.7%), and vomiting (1/13, 7.7%).

  Conclusions  Patients with HER-2 negative advanced breast cancer, with HER-2 mutation, may benefit from anti-HER-2 treatment with pyrotinib.