Introduction/Background To investigate the molecular classification of endometrial carcinoma (EC) and atypical endometrial hyperplasia (AEH) treated with fertility-sparing therapy, and to determine its relationship to oncologic and reproductive outcome.

Methodology Patients who received fertility-sparing therapy and molecular classification tested by next generation sequencing in Hospital Clínic of Barcelona from January 2007 to june 2022 were retrospectively collected. The relationships between molecular classification and clinicopathological factors and treatment outcomes were analyzed.

Results 35 women were included: 22 (62.9%) patients with AEH and 13 (37.1%) with stage IA EC (11 grade 1 and 2 grade 2) Median age of the patients was 36.4 years (range 23–45) and BMI 29.0±6 Kg/m2. The 85% were nulliparous, 60% were infertile and 35% presented abnormal uterine bleeding.

Of the 35 patients, 29 cases (82.9%) had complete response (CR) after treatment, with median CR time of 8 months, 8.6 cases (1%) had partial response, and 6 cases (17%) had recurrence. Only 10 patients (28,6%) underwent definitive surgery.

The global live birth rate was 33%, among patients who attempted to conceive (17), the pregnancy rate was 41.2%. We found a higher rate among patients who underwent fertility treatments (IVFs). There were 14% of spontaneous abortion and 28.6% of IVFs failures.

The cases were distributed as no specific molecular profile (NSMP) 33 cases (94,3%), high microsatellite instability (MSI-H) 2 cases (5,7%), POLE ultra-mutated 0 cases and copy number high (CNH) 0 cases.

Conclusion Fertility-sparing management presented a high response rate in patients with endometrial cancer. Assisted reproductive techniques increase pregnancy rates. Molecular classification is fesible in biopsy of patients with EC and AEH treated with fertility-sparing therapy. However, there are few cases in POLE ultra-mutated and CNH subtypes, which need further clinical research.

Disclosures The authors have nothing to disclose.