Camrelizumab and apatinib in Chinese patients with locally advanced or metastatic radioiodine-refractory differentiated thyroid cancer: an exploratory open-label, single-arm trial

BACKGROUND: Radioactive iodine-refractory differentiated thyroid cancer (RAIR-DTC) remains a therapeutic challenge, especially after progression on prior systemic therapies. While immune checkpoint inhibitors combined with antiangiogenic agents have shown synergy in other tumors, data in RAIR-DTC are limited. This study evaluated camrelizumab plus apatinib in first-line and salvage settings. METHODS: This open-label, single-arm, phase II trial (NCT04560127) enrolled patients with locally advanced or metastatic RAIR-DTC. Patients received intravenous camrelizumab (200 mg every 2 weeks) and oral apatinib (250 mg daily) in 4-week cycle until progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS). Secondary endpoints included objective response rate (ORR), overall survival (OS), disease control rate (DCR), and safety. RESULTS: Between September 2020 and August 2021, 20 patients were enrolled and treated. As of the data cutoff, the median follow-up was 28.4 months (IQR, 22.3-31.2). Median PFS was 11.0 months (95% CI, 6.0-14.2), with 11.6 months (95% CI, 4.8-NE) in treatment-naïve patients and 11.0 months (95% CI, 3.7-19.4) in pretreated patients. Median OS was not reached. The confirmed ORR was 30.0% (95% CI, 11.9-54.3), with 6 patients achieving partial response, and DCR was 95.0% (95% CI, 75.1-99.9). The most common grade ≥ 3 treatment-related adverse events were increased gamma-glutamyltransferase (40.0%) and increased alanine aminotransferase (30.0%). CONCLUSIONS: Camrelizumab plus apatinib demonstrated promising efficacy and manageable toxicity in RAIR-DTC across both first-line and salvage settings, supporting further evaluation as a potential second-line option in the absence of established standard therapies in this setting. TRIAL REGISTRATION: The study was registered at clinicaltrials.gov with the identifier NCT04560127.