The purpose of this study is to evaluate the use of temozolomide alone and with capecitabine in patients with pancreatic neuroendocrine tumors that have spread and are continuing to grow. Both drugs are approved for the treatment of other types of cancer, but their use in this study is considered investigational. They have benefited some patients with pancreatic neuroendocrine tumors, but have never been compared.
In the study, patients will be randomly assigned to receive temozolomide alone or temozolomide and capecitabine. Both drugs are taken orally (by mouth).