Capecitabine and Streptozocin With or Without Cisplatin in Treating Patients With Unresectable or Metastatic Neuroendocrine Tumors

RATIONALE: Drugs used in chemotherapy, such as capecitabine, streptozocin, and cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. It is not yet known whether giving capecitabine together with streptozocin is more effective with or without cisplatin in treating neuroendocrine tumors. PURPOSE: This randomized phase II trial is studying giving capecitabine together with streptozocin to see how well it works compared with or without cisplatin in treating patients with unresectable or metastatic neuroendocrine tumors.