Background: Although the combination of immunotherapy and antiangiogenic agents has been proved a promising strategy in endometrial cancer, studies in Chinese patients are limited. In the earlier phase II study (NCT04157491), Chinese patients with recurrent or advanced endometrial cancer treated with sintilimab + anlotinib had an objective response rate of 73.9% (95% confidence interval [CI]: 51.6% to 89.8%). Here we further updated overall survival (OS) and subsequent therapy for this study. Methods: Patients with endometrial carcinoma progressed after platinum-based chemotherapy were enrolled. Sintilimab 200 mg was supplied intravenously on day one, whereas anlotinib 12 mg was administered orally on day 1 - 14 every three weeks. Results: Twenty-three patients were enrolled in the study. 47.8% of patients received ≥ 2 lines of prior chemotherapy; microsatellite instability-high/mismatch repair deficiency (MSI-H/dMMR) and microsatellite instability stable/mismatch repair proficient (MSS/pMMR) accounted for 39.1% and 60.9% of patients, respectively. We observed a median OS of 17.8 months (95% CI, 9.4 to 26.3 months). Patients with microsatellite instability-high (MSI-H) had superior OS than their counterparts (not available vs. 13.3 months; HR 0.15, 95% CI, 0.33-0.70; P = 0.006). All patients had dropped out of the cohort [56.5% progression disease (PD), 13.0% adverse events (AE)]. Notably, five patients with partial responses (PRs) obtained pathological or radiography complete responses (CRs) in the follow-up. Pathological CRs were confirmed in three patients with long-lasting PRs who underwent surgery, consistent with PET/CT scans. Two patients with PR continued to have tumor shrinkage following treatment cessation due to AE and achieved CR during follow-up. Three out of four patients with CR experienced recurrences. There were no new grade 3-4 AEs associated with therapy. Conclusions: In terms of OS, combining sintilimab and anlotinib had promising therapeutic effects. Pathological CR was observed in patients with long-lasting PR, thus exploratory surgery may be required in selected patients. Clinical trial information: NCT04157491.

^a After PFS achieved 2 years. b After surgery.