Clinicopathological features and survival outcomes in women with endometrial neuroendocrine tumors.

5604 Background: Endometrial neuroendocrine tumors (ENET) are rare, representing about 0.8% of endometrial cancers. Due to their aggressive nature, they are often diagnosed at an advanced stage with no standardized treatment guidelines. This study provides data on the clinicopathological features and survival outcomes of ENETs. Methods: This IRB-approved retrospective cohort study evaluated patients with ENETs seen at MD Anderson Cancer Center between 1994 and 2024. All patients with a histology-confirmed diagnosis of ENET were included. Descriptive statistics was used to summarize patients’ clinicopathologic features. Event-free survival (EFS) was defined as the time from 1st treatment to recurrence, progression, or death. Overall survival (OS) was defined as the time from start of 1st treatment to death. Kaplan-Meier was used to estimate OS and EFS, and Cox regression was used to estimate hazard ratios for prognostic factors. Results: A total of 97 patients were included. Median age at diagnosis was 60 years (range: 30–85). Median BMI was 30.3 kg/m2 (range: 17.1 - 76.7). 87% were white. FIGO stage at diagnosis was 31% stage I/II, 62% stage III/IV, and 5% unknown. 84% underwent primary surgery and 16% had neoadjuvant chemotherapy. For those who underwent surgery, 59% had chemotherapy and 39% had radiotherapy. 39% of patients were NED after completion of primary treatment, 38% progressed and 23% recurred. Median follow-up was 1.4 years (range 6 days to 15.7 years). Median EFS was 0.8 years (95% CI: 0.6–1.3). On multivariate analysis, patients treated with carboplatin/paclitaxel (C/P) (HR= 0.43, 95% CI: 0.24–0.79, p =0.006), or cisplatin/etoposide (C/E) (HR = 0.35, 95% CI: 0.20–0.62, p = 0.001) had a decreased risk of recurrence compared to no adjuvant therapy. Among Stage I/II patients treated with C/E had a decreased risk of recurrence compared to patients treated with C/P (HR= 0.16 (95% CI: 0.03–0.80), p=0.025). Median OS was 1.6 years (95% CI: 1.2–3.0). Multivariate analysis showed stage III/IV disease had almost 3 times the risk of death (p=0.0008). Treatment with C+P (HR =0.40, 95% CI: 0.22–0.74, p=0.003) or C+E had a HR= 0.35 (95% CI: 0.20–0.63), p= 0.0005, compared to patients receiving other or no chemotherapy. Conclusions: This study highlights the aggressive nature of ENETs, often diagnosed at advanced stage. Adjuvant therapy with cisplatin/etoposide was associated with reduced the risk of death compared to other treatments. Despite chemotherapy, median EFS was short, highlighting the need for improved treatment strategies.