A multicenter single-arm study of induction EC/EP plus camrelizumab followed by maintenance camrelizumab plus apatinib in treatment-naive advanced or metastatic extrapulmonary neuroendocrine carcinoma.

4176 Background: Extrapulmonary neuroendocrine carcinoma (EP-NEC) is a poorly differentiated and highly aggressive malignancy with poor prognosis. Platinum (cisplatin or carboplatin) plus etoposide (EC/EP) remains the standard first-line regimen. However, clinical outcomes are suboptimal, highlighting the need for more effective strategies. Camrelizumab is a programmed cell death-1 (PD-1) inhibitor, and apatinib is a vascular endothelial growth factor receptor-2 (VEGFR2) inhibitor. Both have demonstrated antitumor activity in multiple solid tumors. Therefore, we investigated a sequential regimen consisting of induction EC/EP plus camrelizumab followed by maintenance camrelizumab plus apatinib in treatment-naive patients with advanced or metastatic EP-NEC. Methods: This multicenter, single-arm trial enrolled patients with previously untreated advanced or metastatic EP-NEC. Patients received 4–6 cycles of induction therapy with cisplatin (25 mg/m² iv, d1-3, q3w) or carboplatin (AUC = 5 iv, d1, q3w) plus etoposide (100 mg/m² iv, d1-3, q3w) in combination with camrelizumab (200 mg iv, d1, q3w). Patients without disease progression received maintenance camrelizumab (200 mg iv, q3w) plus apatinib (250 mg, qd) until progression or unacceptable toxicity. The primary endpoint was objective response rate (ORR). Secondary endpoints included disease control rate (DCR), progression-free survival (PFS), overall survival (OS), and safety. Tumor response was assessed every 6 weeks per RECIST v1.1. The trial is registered on ClinicalTrials.gov, NCT05142865. Results: As of January 2026, 30 patients were enrolled (median age of 59.5 years, range 30–73), and all 30 patients were evaluable for efficacy. The ORR was 66.7% and the DCR was 83.3%. Median PFS was 9.87 months (95% CI, 6.23–NA). Median OS was not reached, and the 1-year OS rate was 74.6%. All patients experienced adverse events (AEs), with grade ≥3 AEs observed in 43.3% (13/30). Grade ≥3 AEs were mainly hematologic toxicities, including anemia (13.3%), neutropenia (13.3%) and thrombocytopenia (13.3%). Common non-hematologic AEs included elevated transaminases (43.3%), mainly grade 1–2, with grade ≥3 events in 10.0%. Conclusions: Induction EC/EP plus camrelizumab followed by maintenance camrelizumab plus apatinib showed encouraging activity and manageable safety in treatment-naive advanced or metastatic EP-NEC. Further studies are warranted to confirm these findings. Clinical trial information: NCT05142865 .