Abstract
<title>Abstract</title> <p> <bold>Background</bold> Borderline resectable gastric cancer—clinical T4b disease with bulky locoregional lymphadenopathy, oligometastatic liver involvement, or both—remains a major therapeutic challenge because upfront curative resection is often infeasible. We evaluated the efficacy and safety of adebrelimab (anti–PD-L1) plus apatinib (anti–VEGFR-2) and SOX (AASOX) as conversion therapy in this population. <bold>Methods</bold> This single-arm, single-centre, exploratory phase II study enrolled patients with histologically confirmed borderline resectable gastric or gastro-oesophageal junction adenocarcinoma and PD-L1 CPS ≥1. Patients received four 21-day preoperative cycles of AASOX (adebrelimab 200 mg and oxaliplatin 130 mg/m² intravenously on day 1; S-1 40 mg/m² orally twice daily on days 1–14; apatinib 250 mg orally once daily, stopped 28 days before surgery). The primary endpoint was the intention-to-treat (ITT) R0 resection rate (A'Hern single-stage design; one-sided α = 0.05; power = 0.80). Secondary endpoints included pathological complete response, objective response rate (ORR), survival, and safety. <bold>Results</bold> Between January 12, 2024, and January 15, 2026, 31 patients were enrolled. At data cutoff (March 31, 2026), median follow-up was 15.0 months. Eleven patients underwent curative-intent surgery, all achieving R0 resection (ITT R0 rate, 35.5%; 95% CI, 19.2–54.6; one-sided P = 0.033), meeting the primary endpoint. ORR was 61.3%. Median OS was not reached, but survival data were immature (7 deaths). Grade ≥3 treatment-related adverse events occurred in 19 patients (61.3%), most commonly neutropenia (38.7%). No treatment-related deaths or Clavien–Dindo grade ≥III perioperative complications occurred. <bold>Conclusions</bold> AASOX met its primary endpoint, achieving an ITT R0 resection rate of 35.5% with manageable toxicity. Survival outcomes remain immature; these hypothesis-generating findings warrant multicentre randomised evaluation. <bold>Trial registration</bold> The study has been submitted to the Chinese Clinical Trial Registry (ChiCTR) and is currently under review. </p>