Temozolomide With or Without Capecitabine in Treating Patients With Advanced Pancreatic Neuroendocrine Tumors

PRIMARY OBJECTIVES: I. To evaluate progression-free survival (PFS) associated with temozolomide alone or temozolomide and capecitabine in patients with advanced pancreatic neuroendocrine tumors. SECONDARY OBJECTIVES: I. To evaluate response rates (RR) associated with temozolomide alone or temozolomide and capecitabine treatment in patients with advanced pancreatic neuroendocrine tumors. II. To evaluate overall survival (OS) associated with temozolomide alone or temozolomide and capecitabine in patients with advanced pancreatic neuroendocrine tumors. III. To evaluate the toxicity associated with temozolomide alone or temozolomide and capecitabine treatment in patients with advanced pancreatic neuroendocrine tumors. IV. To evaluate the usefulness of methyl guanine methyltransferase (MGMT) status (by immunohistochemistry \[IHC\] and promoter methylation) for predicting response in pancreatic neuroendocrine tumor patients treated with either temozolomide or temozolomide and capecitabine. V. To bank radiology images for evaluation of quality, reproducibility, and compliance with computed tomography (CT) methodology. OUTLINE: Patients are randomized to 1 of 2 treatment arms. ARM A: Patients receive temozolomide orally (PO) once daily (QD) on days 1-5. Treatment repeats every 28 days for up to 13 courses in the absence of disease progression or unacceptable toxicity. ARM B: Patients receive capecitabine PO twice daily (BID) on days 1-14 and temozolomide PO QD on days 10-14. Treatment repeats every 28 days for up to 13 courses in the absence of disease progression or unacceptable toxicity. After completion of study treatment, patients are followed up every 3 months for 2 years, and then every 6 months for 3 years.