Phase III Intergroup Trial of Adjuvant Chemoradiation After Resection of Gastric or Gastroesophageal Adenocarcinoma

RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Radiation therapy uses high-energy x-rays to damage tumor cells. Combining chemotherapy with radiation therapy after surgery may kill any remaining tumor cells following surgery. It is not yet known which chemotherapy and radiation therapy regimen is more effective in treating stomach or esophageal cancer. PURPOSE: Randomized phase III trial to compare two different chemotherapy and radiation therapy regimens in treating patients who have undergone surgery for stomach or esophageal cancer.