Sintilimab Monotherapy in Patients With Stage I-II MSI-H/dMMR Endometrial Cancer

Inclusion criteria

• Aged 18-75 years.
• Histopathologically confirmed endometrial cancer, with pathological types including endometrioid, serous, clear cell, undifferentiated, dedifferentiated, or carcinosarcoma.
• Laboratory-confirmed dMMR (mismatch repair deficient) endometrial cancer (loss of MLH1/PMS2/MSH2/MSH6 protein expression by immunohistochemistry) or MSI-H (microsatellite instability-high by PCR or NGS).
• Stage I-II according to the FIGO 2023 staging system.
• At least one measurable lesion (RECIST 1.1 criteria).
• ECOG performance status 0-1, with a life expectancy of ≥12 months.
• Strong desire for uterine preservation, conservative treatment, or fertility preservation, or inability to tolerate standard surgery due to comorbidities.
• Adequate organ function within 14 days prior to enrollment.
• Good follow-up conditions and signed informed consent.

Exclusion criteria

• Presence of active autoimmune disease, or long-term requirement for immunosuppressive agents;
• Prior treatment with immune checkpoint inhibitors;
• Concurrent persistent or active infections, such as hepatitis B, hepatitis C, etc.;
• Concurrent severe dysfunction of vital organs including heart, lung, liver and kidney: alanine aminotransferase/aspartate aminotransferase elevated more than 3 times the upper limit of normal (ULN) and unresponsive to liver-protective therapy; serum creatinine ≥1.5 × ULN; abnormal thyroid function; history of heart failure, unstable angina pectoris, severe arrhythmia, myocarditis, interstitial lung disease, non-infectious pneumonitis or active pulmonary infection, etc.;
• Other active malignant tumors (except cured basal cell carcinoma of the skin, cervical carcinoma in situ, etc.);
• Known hypersensitivity to any component of the study drug;
• Pregnant or breastfeeding women;
• Any severe or unstable concomitant disease that, in the investigator's judgment, renders the subject ineligible for this study.