Sunitinib is used to treat gastrointestinal stromal tumors in people with tumors that were not treated successfully with imatinib (Gleevec) or people who cannot take imatinib. Sunitinib is also used to treat advanced renal cell carcinoma (a type of cancer that begins in the cells of the kidneys). Sunitinib is also used to treat pancreatic neuroendocrine tumors (a type of tumor that begins in certain cells of the pancreas) in people with tumors that have worsened and cannot be treated with surgery. Sunitinib is in a class of medications called multikinase inhibitors. It works by blocking the action of the abnormal protein that signals cancer cells to multiply. This helps stop or slow the spread of cancer cells and may help shrink tumors.