A phase III study of combination therapy with everolimus plus lanreotide versus everolimus monotherapy for unresectable or recurrent gastroenteropancreatic neuroendocrine tumor (JCOG1901, STARTER-NET).

652 Background: There is limited evidence regarding the benefit of adding somatostatin analogs to molecular targeted agents for well-differentiated gastroenteropancreatic neuroendocrine tumors (GEP-NETs). This phase III trial was conducted to compare everolimus plus lanreotide (EVE/LAN) with everolimus monotherapy (EVE) in patients with unresectable or recurrent GEP-NETs in the first-line setting. Methods: Patients with grade 1 or grade 2, nonfunctioning GEP-NETs with poor prognostic factors (Ki-67 labeling index (LI) 5-20% or diffuse liver metastases) were randomly assigned (1:1) to EVE (10 mg/day) or EVE/LAN (EVE + LAN 120 mg every 28 days). The primary endpoint was progression-free survival (PFS). The key secondary endpoint was overall survival (OS), and other secondary endpoints were objective response rate (ORR), disease control rate (DCR), and safety. The study was based on the hypothesis of an assumed median PFS of 11.0 months for EVE, expecting a 4-month improvement by EVE/LAN (HR: 0.73). The planned sample size was 250, requiring 195 events overall with a one-sided alpha level of 5%, a power of 70%, an accrual period of 5 years, and a follow-up period of 1.5 years. Results: Between April 2020 and June 2024, a total of 178 patients were enrolled, and the planned interim analysis was conducted in 145 patients (72 in the EVE and 73 in the EVE/LAN) in June 2024 with a data cut-off date of Nov 2023. The median PFS was 11.5 months in the EVE arm and 29.7 months in the EVE/LAN arm (HR 0.38 [99.91% CI 0.15–0.96], P = 0.00017 < the prespecified significance level of 0.00046, by the stratified log-rank test). The HR for OS was 0.97 (95% CI: 0.24-3.90). The ORR and DCR were 8.7% (6/69) and 87.0% (60/69) in the EVE arm and 26.8% (19/71) and 91.5% (65/71) in the EVE/LAN arm, respectively. Both hematologic and non-hematologic toxicities tended to be more frequent in the EVE/LAN arm than in the EVE arm. No treatment-related deaths were observed in either arm. Based on the efficacy results, the Data and Safety Monitoring Committee recommended early termination of the study. Conclusions: The EVE/LAN provides statistically significant prolongation of PFS compared with EVE monotherapy, and the safety profile of EVE/LAN was manageable. The EVE/LAN might be a new standard treatment in the first-line setting for well-differentiated grade 1/2 GEP-NETs with poor prognostic factors. Clinical trial information: jRCT1031200023.