Complete response in patient with liver metastasis of HER2-positive breast cancer following therapy with margetuximab: a case report.

Metastatic human epidermal growth factor receptor 2 (HER2) positive breast cancer has a poor prognosis and few effective targeted therapies. However, several anti-HER2 agents are emerging in conjunction with chemotherapy, which may lead to increased rates of pathological complete response in patients with HER2-positive metastatic breast cancer. Among them, margetuximab demonstrated a significant improvement in progression-free survival compared with trastuzumab, when combined with chemotherapy in pretreated patients. Here we present a case of a 67-year-old female patient who was diagnosed with HER2-positive, histological grade III and invasive ductal carcinoma of the left breast in September 2018. She received postoperative adjuvant therapy with EC-TH plus radiotherapy, followed by therapy with HER2-targeted trastuzumab for 1 year (till December 2019). In May 2020, routine reexamination showed a supraclavicular lymph node and bone metastasis. Patient was then treated with pyrotinib, capecitabine and bisphosphonate for a period of 3 months. In December 2020, liver MRI revealed multiple liver metastases. The patient received eight cycles of second-line therapy (vinorelbine plus margetuximab) from January 2021. Since the ninth cycle, the patient was continued with only margetuximab. In March 2021, MRI showed a 70% decrease in the liver metastasis lesions. By June 2021, liver lesions were totally disappeared. During therapy, patient experienced only grade-1 anemia. This case demonstrates that margetuximab plus chemotherapy is safe and might bring clinical benefits for patients with HER2-positive breast cancer with liver metastasis. Further studies evaluating the efficacy and safety of margetuximab in Chinese HER2-positive breast cancer patients are needed.