Study protocol for a multi-institutional randomized phase III study comparing combined everolimus plus lanreotide therapy and everolimus monotherapy in patients with unresectable or recurrent gastroenteropancreatic neuroendocrine tumors; Japan Clinical Oncology Group Study JCOG1901 (STARTER-NET study).

Everolimus is recognized as one of the standard drugs for the treatment of unresectable or recurrent gastroenteropancreatic neuroendocrine tumors (NET). However, recent evidence has suggested that addition of somatostatin analogs to everolimus may yield better survival outcomes as compared to everolimus alone. In April 2020, we have initiated a randomized phase III trial in Japan, to confirm the superiority of combined everolimus plus lanreotide therapy over everolimus monotherapy in patients with unresectable or recurrent gastroenteropancreatic NETs with poor prognostic factors (Ki-67 labeling index: LI 5%-20% or Ki-67 LI < 5% with diffuse liver metastases). We plan to enroll a total of 250 patients from 76 institutions over an accrual period of 5 years. The primary endpoint is progression-free survival. The key secondary endpoint is overall survival, with response rate, disease control rate, and proportion of patients with adverse events as the other secondary endpoints. This trial is registered with the Japan Registry of Clinical Trials as jRCT1031200023 [https://jrct.niph.go.jp/en-latest-detail/jRCT1031200023].