Introduction/Background Non-endometrioid endometrial carcinomas (NEEC) are rare and have poor prognoses. This study aimed to compare the outcomes between open and minimally invasive surgery (MIS) surgery procedures in a cohort of NEEC patients with different prognostic risks based on the risk classification guideline of 2020 ESGO-ESTRO-ESP.

Methodology A retrospective cohort study was conducted of high- and intermediate-risk NEEC patients with surgery treatment at Fujian University Cancer Hospital between January 2011 and January 2018. All cases underwent either open or MIS procedures. OS and DFS were compared between the groups. A nomogram integrating factors, including surgical approaches, LVSI, and adjuvant therapy, was constructed to predict the recurrence probability.

Results There were 31 patients in the MIS group and 68 in the open surgery group. The two groups were comparable in age, body mass index, comorbidity, histologic subtype, and FIGO stage. The MIS group reported ten recurrent cases (1 vaginal, 2 lymph nodes, and 7 distant metastasis). In contrast, seven cases recurred in the open group (1 vaginal, 3 lymph nodes, 1 pelvis, and 2 distant metastasis). The two groups’ high- and intermediate-risk patients showed similar OS (high-risk subgroup’s P=0.275; intermediate-risk subgroup’s P=0.201). However, subgroup analysis showed MIS group displayed poorer DFS in high-risk patients (P=0.001). Multivariate analyses identified besides LVSI, the surgical approach was an independent poor prognostic factor for DFS in high-risk patients (P=0.037, 95%CI: 1.062–7.409). Moreover, the nomogram had a good predictive performance with a 0.855 AUC value.

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Abstract #581 Figure 1

Patient selection. Fig 2 Overall survival in different prognostic risk groups (A) Overall survival in intermediate-risk group (B) Overall survival in high-risk group. Fig 3 Disease free survival in different prognostic risk groups (A) Disease free survival in intermediate-risk group (B) Disease free survival in high-risk group. Fig 4 Nomogram for recurrence risk.

Conclusion To our knowledge, our study is the first to investigate different surgical approaches’ roles on NECC patients based on the new risk classification of ESGO-ESTRO-ESP. Despite possible clinical benefits, MIS should be carefully used for high-risk NEEC patients.

Disclosures The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.