Fertility-sparing treatment outcomes using immune checkpoint inhibitors in endometrial cancer patients with Lynch syndrome.

Objective: To evaluate the efficacy of immune checkpoint inhibitors (ICIs) for fertility-sparing treatment in Lynch syndrome-associated endometrial cancer (LS-EC).

Methods: Four LS-EC cases received programmed cell death protein 1 (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, carrying germline MLH1 mutation, was diagnosed with Stage IIAm_MMRd (International Federation of Gynecology and Obstetrics 2023) endometrial cancer (EC) at 38 years old. She received PD-1 inhibitor treatment and achieved a pathological complete response (CR) at 42 weeks. Case 2, carrying MLH1 mutation, underwent colorectal cancer surgery at 22 years and was diagnosed with EC and synchronous ovarian cancer at 39 years. After 24-week PD-1 treatment, CR of EC and ovarian cancer was achieved. Case 3, carrying MSH2 mutation, was diagnosed with endometrial atypical hyperplasia (EAH) at 35 years. After receiving 7-month progestin, she had the progressed disease with Stage IA2m_MMRd EC and colon cancer was found soon after. She received PD-1 treatment for 18 weeks and achieved a CR of EC. She conceived naturally with full term delivery. Case 4, carrying MSH2 mutation, had a recurrence of Stage IBm_MMRd EC 15 months after CR from EAH treated with progestin at 40 years. She received PD-1 treatment for 18 weeks and achieved CR. No recurrence was found in all cases after 3-41 months of follow-up after CR.

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