Pioneering preoperative anti-PD-1 immunotherapy enables curative resection in dMMR advanced/recurrent endometrial carcinoma: a case series (2020–2022)

Mismatch repair-deficient (dMMR) advanced or recurrent endometrial carcinoma presents a therapeutic challenge, and the role of preoperative immunotherapy prior to its guideline incorporation (2020–2022) remained unexplored. We report three patients with dMMR endometrial carcinoma who received preoperative anti‑PD‑1 therapy (sintilimab). Case 1 (locally recurrent vaginal mass) was treated with sintilimab monotherapy, achieving a pathological complete response. Case 2 (stage IVB with bulky uterine and osseous metastases) received sintilimab combined with carboplatin/docetaxel, attaining partial response. Case 3 (recurrent disease with renal impairment) received sintilimab plus megestrol acetate, which yielded a marked biochemical response (98.6% CA125 reduction) enabling resection despite radiographic stable disease. All patients underwent R0 resection and remained recurrence‑free after a median follow‑up of 36 months, with no grade ≥ 3 adverse events. Exploratory biomarker analysis revealed cGAS‑STING pathway activation in all tumors. These findings provide early real‑world evidence that preoperative anti‑PD‑1 therapy is a feasible and effective strategy for converting unresectable dMMR endometrial carcinoma to resectable disease, supporting further investigation in larger studies.