Novel medical therapies of recurrent and metastatic gastroenteropancreatic neuroendocrine tumors.

Neuroendocrine tumors (NETs) of the gastrointestinal tract and pancreas are slow-growing but commonly advanced malignancies with increasing incidence and prevalence. While locoregional disease can be effectively managed with resection, treatment of recurrent, progressive or metastatic disease has until recently been limited to palliative embolization and cytoreducitve surgery, with cytotoxic chemotherapeutic agents being the last resort. However, novel molecular targeted therapies inhibiting malignant cell proliferation and neoangiogenesis, as well as new cytotoxic chemotherapy drugs and somatostatin analogues, are all being investigated for their potential use in advanced neuroendocrine tumors. Long-acting release forms of octreotide have been shown to not only improve symptoms in carcinoid syndrome but to also delay progression of gastrointestinal NETs. On the other hand, phase III trials have demonstrated everolimus (with octreotide) and sunitinib to increase progression-free survival in pancreatic NETs. Use of bevacizumab has also shown promise in a phase II study, and results of an ongoing phase III trial comparing it to interferon are eagerly expected. Use of radiolabeled somatostatin analogues is still under investigation, though several phase II studies are encouraging. New cytotoxic agents, most notably temozolomide and capecitabine, are already in use, but their relative effectiveness compared to streptozocin in pancreatic NETs is yet to be determined.