Liposomal Irinotecan, Vincristine, Temozolomide, and Anlotinib for R/R Pediatric Solid Tumors

This is a prospective, single-center, single-arm interventional trial conducted at Tianjin Medical University Cancer Institute and Hospital. It evaluates the efficacy and safety of a combination regimen (liposomal irinotecan + vincristine + temozolomide ± anlotinib) in children with relapsed or refractory malignant solid tumors, with the goal of optimizing regimen-related adverse reactions and exploring appropriate administration strategies. 1. Study Objectives Primary Objective: Assess the objective response rate (ORR) of the combination regimen in the study population. Secondary Objectives: Evaluate survival outcomes (progression-free survival \[PFS\], overall survival \[OS\]) and the incidence of adverse events (per NCI CTCAE v5.0). 2. Eligibility Criteria Inclusion Criteria Aged 3-18 years (inclusive) at consent; Pathologically confirmed relapsed or refractory malignant solid tumors (e.g., neuroblastoma, rhabdomyosarcoma); At least one measurable lesion (per RECIST v1.1); Adequate functional status and organ function (per institutional standards); Written informed consent from subject/legal guardian. Exclusion Criteria Hypersensitivity to study drugs; Active uncontrolled infection or severe comorbidities; Concurrent participation in other interventional trials; Conditions precluding study participation (per investigator judgment). 3. Intervention Procedures Eligible subjects are assigned to short-course or long-course subgroups based on clinical status: Short-course: Liposomal irinotecan (Day 1), vincristine (Day 1), temozolomide (Days 1-5), ± weight-based anlotinib (Days 1-14); Long-course: Liposomal irinotecan (Days 1/8/15), plus the same doses of other drugs as the short-course subgroup. Each treatment cycle is 21 days. Efficacy is assessed regularly; treatment (dose/subgroup) will be adjusted per clinical condition. 4. Outcome Assessments Primary Outcome: ORR (assessed per RECIST v1.1 at regular intervals); Secondary Outcomes: PFS, OS (long-