3436 - Multivariate Analysis of Outcomes of Palliative Radiotherapy and Re-Irradiation in Children

Purpose/Objective(s): Data regarding palliative radiotherapy (PRT) in children is limited, and current practice is often extrapolated from adult studies. We aimed to analyze the clinical outcomes of PRT and palliative reirradiation in children.

Materials/Methods: Patients aged =21 years treated with PRT for malignancy at a single institution were included. A retrospective review of medical records was done. Progression-free survival (PFS) was measured until local progression, death, or censoring, and overall survival (OS) was measured until death or censoring from the first day of PRT. Time-to-event analyses were done using the Kaplan-Meier method. Univariate and multivariate (MVA) analyses were done using the Cox proportional hazards model for sex, age, interval between initial radiotherapy (RT) and PRT, diagnosis, indication, RT site, technique, dose, dose per fraction, staggered fractionation scheme (higher dose per fraction for early fractions of PRT, followed by lower doses per fraction), resection before PRT, systemic therapy during PRT, and symptomatic relief. Adverse events were graded using the CTCAE v6.0.

Results: Between Jan 1, 2010, and Aug 2, 2024, 118 courses of PRT were delivered in 53 patients. Median age at PRT was 9 years (IQR 7–19); 62% were female. The most common diagnoses were Ewing sarcoma (26%), rhabdomyosarcoma (14%) and neuroblastoma (13%). The most common indications were pain (49%) and spinal cord compression (25%). The most common sites were spine (30%) and brain (14%). Techniques included 3-dimensional conformal RT (86%), intensity-modulated RT (10%), and stereotactic body RT (4%). The median dose was 20 Gy (IQR 8–20) in 5 fractions (IQR 3-5); 101 (86%) had fraction sizes >2 Gy. At data cut-off (Oct 5, 2024), the median follow-up time was 58.0 months (IQR 34.3-62.2). Symptomatic relief occurred in 72% of courses. The 3- and 6-month PFS was 67.6% (95% CI 57.6–75.8) and 43.1% (33.4-52.5), respectively. The 3- and 6-month OS was 61.6% (95% CI 52.1–69.7) and 41.0% (32.1–49.8), respectively. In 14 courses of palliative re-irradiation, 80% of patients had symptomatic relief, 3- and 6-month PFS was 44.4% (95% CI 13.6–71.9) and 22.2% (3.4–51.3), respectively, and 3- and 6-month OS was 71.4% (40.6–88.2) and 50.0% (22.9–72.2), respectively, from the first day of re-irradiation. In MVA, PFS was associated with staggered fractionation (HR 2.87, 95% CI 1.00–8.22, p=0.049), systemic therapy during PRT (HR 0.48, 0.26–0.90, p=0.022) and PRT for asymptomatic lesions (HR 0.50, 0.28–0.90, p=0.020). Grade 2–3 acute toxicity occurred in 9.3% of treatment courses. 5 patients had grade 3 acute toxicities, 3 esophagitis and 2 pain flare, all requiring hospitalization. No grade 4 or higher acute or any late toxicity was observed.

Conclusion: Palliative RT provides symptomatic relief and is well tolerated in children, even if patients require palliative reirradiation with =2 courses to the same anatomic site.