Combination Chemotherapy and Intensity-Modulated Radiation Therapy in Treating Patients Undergoing Surgery for Locally Advanced Rectal Cancer

RATIONALE: Drugs used in chemotherapy work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Specialized radiation therapy that delivers a high dose of radiation directly to the tumor may kill more tumor cells and cause less damage to normal tissue. Giving these treatments before surgery may make the tumor smaller and reduce the amount of normal tissue that needs to be removed. Giving chemotherapy after surgery may kill any tumor cells that remain after surgery.
PURPOSE: This phase II trial is studying the side effects and how well giving combination chemotherapy together with intensity-modulated radiation therapy works in treating patients undergoing surgery for locally advanced rectal cancer.