Case Report: Immunotherapy-containing fertility-sparing treatment integrated with preimplantation genetic testing resulting in live birth in Lynch syndrome-associated endometrial cancer.

BACKGROUND: Lynch syndrome-associated endometrial cancer (LS-EC) presents unique challenges for fertility preservation. Conventional progestin-based therapy may be less effective in mismatch repair-deficient (MMRd) tumors, whereas immune checkpoint inhibitors (ICIs) have shown promising activity. Meanwhile, preimplantation genetic testing for monogenic disorders (PGT-M) offers a way to prevent hereditary transmission. CASE PRESENTATION: A woman was initially diagnosed with complex atypical hyperplasia at age 28 and subsequently developed presumed FIGO 2009 stage IA endometrial cancer (EC) associated with a germline pathogenic variant in MSH2. After failing to achieve complete response (CR) following prolonged progestin therapy, she received multimodal fertility-sparing treatment comprising a programmed cell death protein 1 (PD-1) inhibitor (sintilimab 200 mg, 9 cycles) in combination with leuprorelin acetate and a levonorgestrel-releasing intrauterine system. This multimodal regimen achieved CR. After sustained remission was confirmed, PGT-M was performed and transfer of an embryo free of the familial pathogenic variant resulted in a healthy live birth. CONCLUSION: This case illustrates the feasibility of integrating immunotherapy-containing fertility-sparing treatment with PGT-M to achieve sustained oncologic control while preventing hereditary transmission in carefully selected patients with LS-EC.