Avastin is used with chemotherapy to treat cancer of the colon (large intestine) or rectum that has spread to other parts of the body. Avastin is also used with chemotherapy to treat certain types of lung cancer. Avastin is also used to treat glioblastoma (a certain type of cancerous brain tumor) that has been already treated with other medications. Avastin is also used in combination with another medication to treat renal cell cancer (RCC, a type of cancer that begins in the kidney) that has spread to other parts of the body. 

Blood vessels supply nutrients and oxygen to tumors. Avastin slows the growth and spread of tumors by stopping the formation of blood vessels that feed the tumors. Avastin is in a class of medicines called antiangiogenic agents.