Perioperative Disitamab Vedotin Plus Toripalimab and XELOX in Gastric or Gastroesophageal Junction Adenocarcinoma.

This study is testing a combination of cancer treatments — including a targeted antibody-drug (disitamab vedotin), an immunotherapy drug (toripalimab), and standard chemotherapy — given before and after surgery for stomach or gastroesophageal junction cancer. The goal is to see if this combination can shrink the tumor before surgery and reduce the chance of the cancer coming back. **You may be eligible if...** - You are 18 years or older - You have been diagnosed with stomach cancer or cancer at the junction of the stomach and esophagus - Your cancer has not spread to distant organs - Surgery to remove the cancer is planned and expected to be curative - You have not received any prior cancer treatment for this condition - Your HER2 protein levels show any level of expression (1+, 2+, or 3+) - Your heart, liver, kidney, and blood counts are within acceptable levels **You may NOT be eligible if...** - You have already received treatment for this cancer - Your cancer has spread to distant organs - You have significant heart, liver, or kidney problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.