A Case of Breast Cancer Achieving pCR after Pembrolizumab + Paclitaxel + Carboplatin Therapy Despite Developing irAE

Abstract

We report the case of a 77-year-old female patient whose main affliction upon presenting at our hospital was a tumor in the right breast. She was diagnosed with cT4bN0M0 Stage IIIB, triple-negative, cancer of the right breast. She was initiated on neoadjuvant therapy consisting of a pembrolizumab + paclitaxel + carboplatin regimen. During the 4^th cycle of treatment, the patient complained of fever, fatigue, and exertional dyspnea. After blood tests and a contrast-enhanced computed tomography scan, she was diagnosed with a pulmonary embolism, drug-induced lung injury, and pituitary inflammation, suggesting an immune-related adverse event (irAE) caused by pembrolizumab. After the administration of an anticoagulant and a steroid pulse, the symptoms improved. The patient was discharged on the 17^th day of hospitalization. The neoadjuvant therapy was discontinued, and two months after the onset of the irAE, a right breast total mastectomy and sentinel lymph node biopsy were performed. Pathological examination revealed no viable tumor cells.

Because pembrolizumab combination therapy is the standard care for triple negative breast cancer, irAEs should be considered. In this case, the neoadjuvant therapy was discontinued due to irAE, but pCR was nonetheless achieved. The treatment strategy should be determined based on the severity of the irAE and the therapeutic effect of the adjuvant therapy.