Case of Triple-negative Breast Cancer that Died of Brain Metastasis Nine Month after Achieving a Pathological Complete Response with Neoadjuvant Chemotherapy

Abstract

A 39-year-old woman was diagnosed with right breast cancer (invasive ductal carcinoma, triple-negative, MIB-1 labeling index of approximately 80%, T2N1M0, stage IIB). Four courses of epirubicin/cyclophosphamide were administered as neoadjuvant chemotherapy, followed by 12 courses of weekly paclitaxel. Subsequent contrast-enhanced computed tomography (CT) revealed a partial response. We speculated that radical surgery was possible and performed right mastectomy with level II axillary lymph node dissection. Histopathological examination of the surgical specimen revealed a pathological complete response. CT and magnetic resonance imaging performed 6 months post-surgery revealed brain metastasis, measuring approximately 26 mm in the right temporal lobe. Considering that she had a single brain metastasis and no metastatic lesions in other organs, we performed intracranial tumor resection followed by whole-brain irradiation. However, the patient died 2 months later. Patients with breast cancer may develop minor brain metastases, and neoadjuvant chemotherapy may have a marked effect on tumors other than those in the brain, but the administered antineoplastic drugs could not cross the blood-brain barrier. Therefore, the brain metastasis that occurred in our patient continued to develop and remained untreated but became apparent post-surgically.