This study is an open-label, single-arm, multicenter, phase 2 clinical trial. Eligible patients are with previously untreated gastric and gastroesophageal junction adenocarcinoma as defined by cT2-4 and/or cN+ without evidence of metastatic disease. Study treatment in this study is neoadjuvant treatment with the investigational drug, T-DXd alone, followed by surgery. T-DXd will be administered at a dose of 6.4 mg/kg (decimal) by intravenous infusion every 21 days (3 weeks) for 3 cycles as the neoadjuvant treatment followed by surgery.~The analyses will be performed on the following 2 cohorts:~Gastric cancer or gastroesophageal junction cancer with HER2 overexpression (IHC3+, or IHC2+ and ISH positive [FISH or DISH]) (Primary cohort)~Gastric or gastroesophageal junction cancer patients with HER2 low expression (IHC1+, or IHC2+ and ISH-negative [FISH or DISH]) and HER2-ECD > 11.6 ng/mL (Exploratory cohort)
This study is an open-label, single-arm, multicenter, Phase 2 study to evaluate the efficacy and safety of neoadjuvant chemotherapy with T-DXd monotherapy in patients with HER2-positive gastric cancer.