29P First-line of camrelizumab, apatinib mesylate and chemotherapy for advanced high-grade neuroendocrine tumors (NETS): A single center, single arm, exploratory study

NETS is a rare subtype cancer with a poor prognosis. Etoposide plus platinum-based chemotherapy, the most frequently used first-line treatment for NETS, results in poor survival (median overall survival OS 11 to 19 months). Camrelizumab combined with apatinib mesylate had improved outcomes across tumor types; little is known about the efficacy in NETS. Patients were eligible if they were aged 18 through 75 years; had histologically or cytologically confirmed high-grade NETS with TNM clinical stage IIIB-IV; had received no previous systemic therapy; Camrelizumab (200mg, every 21 days) and apatinib mesylate (250mg, everyday) were given until disease progression, Etoposide (100mg/m2, d1-3) and cisplatin(25mg/m2, d1-3) were given for up to 6 cycles. The primary endpoint was progression free survival (PFS) defined by the RECIST 1.1 guideline. 12 patients were enrolled from July 19, 2021 to May 24, 2023. The median age was 61 years (range, 58-68). 7 patients were males (58.3%) and 5 females (41.7%). The Eastern Cooperative Oncology Group performance status score was 0 in 8 patients (66.7%) and 1 in 4 patients (33.3%). The tumors were primarily located in the mediastinum for 4 patients (33.33%), skin for 2 patients (16.7%), and in the parotid gland, lung, descending colon, nasal cavity, stomach's cardia, and ureter, with one patient (8.3%) in each location. All patients showed a Ki-67 index of over 55%. 11 underwent efficacy evaluation, including 9 partial response, 1 stable disease, and 1 progression disease. The objective response rate was 81.8%, and the disease control rate was 90.9%. At data cutoff, 8 of 12 patients experienced disease progression, with a median PFS of 10.7 months. The median OS has not yet been reached. Adverse events occurred in 10 (83.3%) patients, the most grade 1-2. Only one patient (8.3%) experienced grade 4 thrombocytopenia. Camrelizumab combined with apatinib mesylate and chemotherapy achieved high response rate and longer median progression free survival in the treatment of newly diagnosed advanced high-grade NETS, with good safety.