Optimal first-line treatment strategies of systemic therapy for unresectable gastrointestinal neuroendocrine tumors based on the opinions of Japanese experts

Background: There are several options for systemic therapy of gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN), including somatostatin analogues (SSA), molecular-targeted agents, cytotoxic agents, and peptide receptor radionuclide therapy. However, the effectiveness of each agent varies according to the primary site. Although SSA and everolimus are key drugs used for systemic therapy of neuroendocrine tumors arising from the gastrointestinal tract (GI-NET), the optimal strategy for selecting among these modalities remains unexplored. Methods Japanese experts on GI-NET discussed and determined optimal first-line treatment strategies based on the results of previously reported pivotal trials. Results The consensus was reached that tumor aggressiveness and prognosis can be predicted using hepatic tumor load and Ki-67 labeling index, which are thought to be clinically important factors when selecting systemic therapy for unresectable GI-NET. SSA therapy is considered appropriate for patients with a low hepatic tumor load and low Ki-67 value and everolimus for those with contraindications to SSA therapy. There was also agreement that the treatment strategy should be determined according to whether the origin is in the midgut, considering the biological differences. Based on this strategy, the experts have tentatively created treatment maps and applied them in representative cases of unresectable GI-NET. Conclusion Japanese experts proposed tentative maps for optimal first-line treatment in patients with unresectable GI-NET. Further investigation is warranted to validate the usefulness of these maps.