Combined Large Cell Neuroendocrine Carcinoma of the Endometrium Treated With Paclitaxel, Carboplatin, and Durvalumab, Followed by Maintenance Therapy With Durvalumab and Olaparib ( <scp>DUO</scp> ‐E Regimen): A Case Report

Combined large cell neuroendocrine carcinoma (LCNEC) of the endometrium is rare and carries a poor prognosis. A 61-year-old woman with suspected endometrial serous carcinoma was referred to our hospital. Imaging studies staged the disease as stage IIIC1. We performed a total hysterectomy, bilateral salpingo-oophorectomy, omentectomy, and retroperitoneal lymph node dissection. Histopathological examination revealed a combination of LCNEC, endometrioid carcinoma, and multiple lymph node metastases. Postoperative computed tomography showed multiple pulmonary metastases not detected preoperatively. Given the advanced and recurrent nature of the disease, treatment with paclitaxel, carboplatin, and durvalumab was initiated. After the first cycle, the pulmonary metastases disappeared. Maintenance therapy with durvalumab and olaparib was continued because of proficient mismatch repair status. This case demonstrates that durvalumab may be a viable treatment option for endometrial LCNEC, as it is also approved for small cell lung cancer, which shares similarities with neuroendocrine carcinoma.