<qa>  What drug can block tumor growth?RATIONALE: Drugs used in chemotherapy, such as capecitabine, irinotecan, and oxaliplatin, 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 may kill more tumor cells. Monoclonal antibodies, such as bevacizumab, can block tumor growth in different ways. Some find tumor cells and kill them or carry tumor-killing substances to them. Others interfere with the ability of tumor cells to grow and spread. Bevacizumab may also block blood flow to the tumor. Giving combination chemotherapy together with bevacizumab may kill more tumor cells. 