Real-world clinical outcomes and safety of anlotinib-containing regimens in pediatric solid tumors: a retrospective cohort study at a Chinese center.

Background and aim: This retrospective cohort study aimed to characterize the real-world clinical outcomes and treatment-emergent adverse events (TEAEs) of anlotinib-containing regimens among pediatric patients with solid tumors treated at the Children's Hospital of Zhejiang University School of Medicine from January 2020 to May 2025. Methods: This retrospective cohort study included 45 eligible patients treated with anlotinib at the Children's Hospital of Zhejiang University School of Medicine from January 2020 to May 2025; eligibility required age <18 years at solid tumor diagnosis, first-time anlotinib use at our center, RECIST 1.1-measurable disease, and available clinical and imaging data. Progression-free survival (PFS) was the primary endpoint, and objective response rate (ORR), disease control rate (DCR), and overall survival (OS) were secondary endpoints. Safety was assessed using the Common Terminology Criteria for Adverse Events version 5.0 (CTCAE v5.0). Results: The observed ORR was 8.9% (4/45), and the DCR was 40.0% (18/45; 4 partial responses and 14 cases of stable disease). The median PFS was 5.6 months (95% CI: 2.9-8.3), while the median OS was not reached after seven deaths. Patients with other solid tumors (n=21) had an ORR of 19.0%, a DCR of 57.1%, and a median PFS of 9.4 months, compared with 0%, 25.0%, and 3.0 months, respectively, among patients with sarcomas (n=24). The observed DCR was 80.0% among patients without metastatic or recurrent disease (n=10) and 28.6% among those with metastatic or recurrent disease (n=35). DCRs were 33.3%, 48.0%, and 0% in the usual-dose (n=18), low-dose (n=25), and high-dose (n=2) groups, respectively; exploratory analyses did not detect statistically significant differences in DCR (p=0.393) or PFS distributions (p=0.395) across the three groups. Exploratory analyses did not detect statistically significant differences across the treatment-regimen groups in ORR (p=0.133), DCR (p=0.454), or PFS distributions (p=0.480). TEAEs were documented in 97.8% of patients, with grade 3-4 TEAEs observed in 84.4%. Hematologic TEAEs were the most frequently documented category (91.1%). Frequent non-hematologic events included pyrexia (62.2%), proteinuria (35.6%), hypokalemia (33.3%), and hypoalbuminemia (33.3%). Conclusion: In this small, heterogeneous, single-center Chinese pediatric cohort, patients receiving anlotinib-containing regimens had limited objective response and a high incidence of grade 3-4 TEAEs, predominantly involving hematologic events. Subgroup findings were exploratory and may reflect selection bias, confounding by indication, tumor heterogeneity, and concomitant therapies. Larger prospective studies are required before comparative treatment or dosing conclusions can be made.