Lymph node involvement, surgery and adjuvant treatment in primary Endometrioid Ovarian carcinoma PAtients with eaRly-stage Disease (LEOPARD) - a multinational team initiative.

OBJECTIVE: Endometrioid ovarian carcinoma (ENOC) is increasingly recognized as a distinct disease entity, yet treatment still largely parallels high-grade serous disease management. We aimed to assemble a large, well-annotated ENOC cohort allowing us to study real-world treatment patterns with special interest on lymph node (LN) metastasis in presumed early-stage disease. METHODS: ENOC cases from 22 centers across five countries underwent IHC-supported central pathology review. Standardized chart review captured patient characteristics, detailed surgical and adjuvant treatment data. RESULTS: A total of 721 centrally confirmed ENOC cases diagnosed between 1984 and 2020 was assembled. Median age was 55.6 years; 86.0% presented with pelvic-confined disease, and 45.1% had grade 1 tumors. Complete resection was achieved in 96.5% of pT1/2 and 62.6% of pT3 cases. LN surgery (LNS) was performed in 58.3% of presumed early-stage cases, revealing nodal metastases in 2.6%, occurring in 4/255 (1.6%) after sampling and 5/95 (5.3%) after systematic LNS. No nodal metastases were observed in grade 1 pelvic-confined tumors (0/171). Adjuvant chemotherapy was administered in 68.0% of FIGOI/II cases and 95.5% of advanced-stage disease. Multivariable analyses revealed grade (p = 0.0006), stage (p = 0.0030) and chemotherapy (p = 0.0219) as independent prognosticators. CONCLUSIONS: This multinational initiative enabled detailed analyses in a large cohort of validated ENOC. According to our results, LNS may be safely omitted in patients with pelvic-confined G1 tumors, however, if LNS is deemed necessary, a systematic approach seems to result in higher detection rates. The findings presented herein may help to shape type-specific treatment, ultimately aiming to reduce not only ovarian carcinoma mortality but also treatment-associated morbidity.