Objectives Undifferentiated and dedifferentiated endometrial carcinomas (UEC/DDEC) are rare, high grade, and have only been increasingly recognized within the past decade. Studies of their behavior and response to adjuvant to guide prognostication and management are limited. We present the management experience of a single institution.

Methods Using the Juravinski Hospital electronic medical record, we identified all patients with UEC or DDEC treated at our institution from January 2005-December 2020. Clinical information was obtained by chart review.

Results We identified 35 patients with UEC/DDEC; 15 UEC, 20 DDEC. Mean age was 66 years. Only 25.1% had preoperative endometrial biopsy concordant with final pathology despite 87.5% review by gynecologic pathologists. Stage distribution was 37.1% stage I, 14.3% stage II, 14.3% stage III, 34.3% stage IV. 7/33 (21.2%) had gross residual after surgery; 4 received adjuvant carboplatin-paclitaxel chemotherapy with 2 progressions, 1 partial response and 1 complete response (ORR 50%). Mean PFS was 11.7±9.3 months. Fifteen patients had progressive or recurrent disease—of these, 4 were treated with radiation, 3 with chemotherapy (adriamycin, carboplatin-paclitaxel, doxorubicin), and all 7 progressed on treatment. The most common site of recurrence was widely disseminated disease (54.5%), followed by nodal (18.2%) and chest (18.2%). Mean OS was as follows by stage: stage I-II completely resected, 43 months; stage III completely resected, 19 months; stage IV, suboptimally debulked or inoperable, 20 months.

Conclusions UEC/DDEC are aggressive tumours with poor prognoses and remain challenging to diagnose on preoperative biopsy. Platinum-based adjuvant chemotherapy may have some efficacy, however, recurrences respond poorly to salvage.