Trastuzumab monotherapy for bone marrow metastasis of breast cancer: A case report

The current study presents the case of a 41-year-old female patient who received modified radical mastectomy and adjuvant chemotherapy and radiotherapy for infiltrating ductal cancer of the left breast. The pathological stage of the disease was IIA. In addition, the patient was negative for the estrogen and progesterone receptors, and human epidermal growth factor receptor-2 gene amplification was identified. At one year following surgery, the patient presented with severe pancytopenia and pain at multiple sites all over the body. Furthermore, the patient's Eastern Cooperative Oncology Group performance status score was 3 and numeric rating scale pain score was 8. The bone marrow puncture indicated bone marrow metastatic cancer, and the positron emission tomography/computed tomography (CT) indicated multiple internal organ metastases and osseous metastasis. Chemotherapy treatment posed great risks due to the patient's poor performance status and severe bone marrow suppression. Therefore, trastuzumab monotherapy was administered at a loading dose of 8 mg/kg and a maintenance dose of 6 mg/kg every three weeks. Following four doses of trastuzumab treatment, the patient's performance status significantly improved and the peripheral blood cell counts had returned to within the normal ranges. Taxol was added to the trastuzumab treatment and seven cycles were completed. No metastatic cancer cells were found in the subsequent bone marrow smear test; however, CT showed metastatic foci in the left lung. Furthermore, the enlarged lymph nodes had subsided and the tumor in the right appendix region had decreased in size by 50%. The patient's disease condition was maintained stable for 11 months.