Abstract
BACKGROUND: Overexpression of human epidermal growth factor receptor 2 (HER2) is associated with aggressive disease and poor prognosis. Traditional HER2-targeted agents can improve clinical outcome and have played an essential role in therapy. Pyrotinib is a newly irreversible tyrosine kinase inhibitor (TKI) that is well developed for the treatment of HER2-positive advanced breast tumors. CASE PRESENTATION: A 37-year-old postpartum female was presented at a local hospital and was diagnosed with HER2-positive stage IIIB (cT4N1M0) invasive micropapillary adenocarcinoma in the left breast with left axillary metastatic lymph nodes. The patient failed to respond to two cycles of the doxorubicin plus cyclophosphamide (AC) regimen but achieved clinical partial response (cPR) after 4 cycles of the combination of pyrotinib, trastuzumab, paclitaxel and cisplatin (PTPC) regimen according to radiologic assessments. Then, she underwent left-side modified radical mastectomy (MRM) and achieved pathologic complete response (pCR), as confirmed by postoperative pathology. The patient held on receiving 2 cycles of the targeted therapy plus chemotherapy with trastuzumab, paclitaxel plus cisplatin (TPC) and adjuvant radiation therapy but continued to receive targeted therapy with trastuzumab and pertuzumab during the 1-year follow-up period. There has been no clinical evidence of disease progression so far. CONCLUSION: Breast cancer overexpressing HER2 is a malignant tumor responsible for many cancer-related deaths. The combination of pyrotinib plus other targeted chemotherapy can dramatically improve the outcome of locally advanced disease.