RATIONALE: Drugs used in chemotherapy, such as oxaliplatin, leucovorin, and fluorouracil, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving more than one drug (combination chemotherapy) before surgery may kill more tumor cells and may make the tumor smaller and reduce the amount of normal tissue that needs to be removed. Giving oxaliplatin, leucovorin, and fluorouracil after surgery may kill any tumor cells that remain after surgery.