Complete response after treatment of breast cancer with isolated liver metastasis: a case report

Background: Breast cancer has a high incidence and is prone to metastasis, while isolated liver metastasis is rare. A growing body of evidence supports the effectiveness of treating breast cancer with anti-human epidermal growth factor receptor-2 (HER2) therapy in combination with chemotherapy. However, little is known about its impact on metastatic liver disease. There is also a lack of consensus on managing liver metastases from breast cancer, and no studies have been conducted on managing the disappearance of liver metastases after treatment. Case Description: In May 2021, a 51-year-old female patient with HER2-positive breast cancer with isolated liver metastases had immunohistochemistry of estrogen receptor (ER) (-), progesterone receptor (PR) (-), and HER2 (3+) for both her primary lesion and liver metastases. After undergoing 17 cycles of anti-HER2 therapy and chemotherapy, the patient expressed a desire for surgery. Then a preoperative examination was performed, which revealed the disappearance of both the primary breast lesion and the liver metastases. Immediately afterwards, a left mastectomy was performed, and postoperative pathology showed a complete response to the breast tumor. As for the liver, where the metastatic lesions disappeared, no relevant study has reported how to deal with this situation. Finally, after a hospital-wide discussion, the patient was given trastuzumab maintenance therapy. Until now, no obvious signs of recurrence or metastasis have been observed during regular follow-ups. Conclusions: This case suggests that maintenance therapy may be the best option for patients with breast cancer whose liver metastases disappear by medication. Also, it can be inferred that in HER2-positive metastatic breast cancer (MBC), patients with isolated liver metastases may be more likely to achieve a curelike outcome. Nevertheless, more cases and follow-up information are needed to support these views.