Introduction/Background Immune checkpoint inhibitors (ICIs) have been proved to be effective in treating advanced or recurrent endometrial cancer (EC) with mismatch repair deficiency (dMMR). However, the efficacy of ICIs on fertility-sparing treatment in dMMR EC has not been reported. Here, we report fertility preserving treatment outcomes in three EC cases with Lynch syndrome (LS) using programmed cell death protein 1 (PD-1) inhibitors.

Methodology Three EC cases with LS received PD-1 inhibitors for fertility preservation at the Obstetrics and Gynecology Hospital of Fudan University from 2017 to 2023. The clinical data and long-term outcomes were retrospectively reviewed.

Results Case 1 carried germline MSH2 mutation, was diagnosed with endometrial atypical hyperplasia (EAH) at the age of 35. After receiving oral progestin for 7 months, she had the progressed disease with stage I (FIGO 2009) EC and colon cancer was found soon after. She received PD-1 inhibitor treatment for 18 weeks followed by radical transverse colon resection and hysteroscopy which revealed a pathological complete response (CR) of EC. The patient received no further treatment and conceived naturally with full term delivery. Case 2 carried MLH1 mutation, underwent colorectal cancer surgery at the age of 22 and was diagnosed with EC and synchronous ovarian cancer at 39y. After PD-1 treatment for 24 weeks, a pathological CR of EC and radiological relieve of ovarian cancer was achieved and she continued immunotherapy for another 18.7 months. Case 3 carried MLH1 mutation, was diagnosed with stage II EC at 38. She received PD-1 inhibitor treatment and achieved CR at 42 weeks. No recurrence was found in all cases after 15–41 months of follow-up after CR.

Conclusion ICIs might be an effective choice for EC patients with LS desiring fertility preservation.

Disclosures There are no potential conflicts of interest to disclose.