Ropivacaine-Poloxamer 407 Gel for Pain Control After Open Gastrectomy

This study is testing a slow-release local anesthetic gel (ropivacaine mixed with poloxamer 407) placed inside the abdomen during stomach cancer surgery to see if it reduces pain better than standard pain management after surgery. The gel gradually releases pain medication over time, potentially reducing the need for stronger pain drugs like opioids. **You may be eligible if...** - You have been diagnosed with stomach cancer (gastric adenocarcinoma) confirmed by biopsy - You had complete surgical removal of your stomach tumor (R0 resection) - You are 20 years of age or older - Your general health rating (ASA score) is 3 or below **You may NOT be eligible if...** - You are under 19 years of age - Your cancer has spread to the lining of the abdomen (peritoneal metastasis) or you have fluid in the abdomen - You had chemotherapy or radiation before surgery - You have another type of cancer - You have uncontrolled diabetes, autoimmune conditions, or a history of problematic scarring - You are allergic to local anesthetics - You are pregnant Talk to your doctor to see if this trial is right for you.