Long-term disease-free survival with chemotherapy and pembrolizumab in a patient with unmeasurable, advanced stage dedifferentiated endometrial carcinoma.

Dedifferentiated endometrial carcinoma is a rare, highly aggressive subtype of endometrial cancer associated with poor survival outcomes. Current guidelines recommend treatment of advanced-stage disease with surgical staging or cytoreduction and platinum/taxane-based chemotherapy. Despite these approaches, the achievement of long-term remission or prolonged survival is challenging. Recent Phase III studies demonstrate that the addition of PD-1 inhibitors to standard chemotherapy significantly improves progression-free survival in patients with measurable, mismatch repair deficient (dMMR) and proficient (pMMR) advanced-stage or recurrent endometrial carcinoma. However, the role of PD-1 blockade in the treatment of undifferentiated and dedifferentiated endometrial carcinoma remains unclear, as very few patients with these cancer subtypes were included in the trials. In this case report, we present a patient with dMMR dedifferentiated endometrial carcinoma, treated with primary surgery to no gross residual disease, followed by carboplatin/paclitaxel chemotherapy and a short course of maintenance pembrolizumab. To date, the patient remains with a prolonged disease-free survival of 61 months, supporting the potential use of PD-1 inhibitors in the upfront treatment of unmeasurable, advanced-stage, dMMR dedifferentiated endometrial carcinoma.