Adjuvant Capecitabine Versus Observation Alone in Curatively Resected Stage IB Gastric Cancer((KCSG ST14-05): CATALYSIS

This study is comparing whether taking a chemotherapy drug called capecitabine (a pill) after surgery for stomach cancer helps prevent the cancer from coming back, compared to no additional treatment after surgery. **You may be eligible if...** - You have been diagnosed with stomach cancer and had surgery to remove the tumor with no detectable cancer remaining - You have fully recovered from surgery and are healthy enough for further treatment - You are at least 18 years old - Your blood counts and organ function are within acceptable ranges **You may NOT be eligible if...** - You have had prior chemotherapy or radiation for this cancer before surgery - You have evidence that cancer is still present or has spread after surgery - You have significant heart, liver, or kidney problems - You are pregnant or breastfeeding - You have had a previous allergic reaction to capecitabine or similar drugs (like 5-fluorouracil) - You have another active cancer diagnosis Talk to your doctor to see if this trial is right for you.