OUTLINE: This is a randomized study. Patients are stratified by tumor stage, age, type of surgery, and participating institution. Patients are randomly assigned to one of two groups. The first group receives radiotherapy to the tumor over 5 weeks and concomitant fluorouracil/leucovorin for 5 consecutive days on the first and fifth weeks. Four to six weeks later, patients undergo complete resection, followed upon recovery by fluorouracil/leucovorin every 4 weeks for 6 courses. The second group receives preoperative chemoradiotherapy followed by surgery, as above, with no postoperative treatment. Patients are followed for survival.