Clinical outcomes and efficacy of stereotactic body radiation therapy in children, adolescents, and young adults with metastatic solid tumors

Objective: The objective of this study is to report disease outcomes and toxicity with the use of stereotactic body radiation therapy (SBRT) in the treatment of pediatric metastatic disease. Methods: All pediatric and adolescent young adult (AYA) patients' who received SBRT were included between the years 2000 and 2020. Study endpoints included local control (LC), progression -free survival (PFS), overall survival (OS), cumulative incidence (CI) of death or local failure and toxicity. The end points with respect to survival and LC were calculated using the Kaplan-Meier estimate. The cumulative incidence of local failure was calculated using death as a competing risk. Results: 16 patients with 36 lesions irradiated met inclusion criteria and formed the study cohort. The median OS and PFS for the entire cohort were 17 months and 15.7 months, respectively. The 1 year OS for the entire cohort was 75%. The 6-and 12 month local control was 85 and 78%, respectively. There were no local failures in irradiated lesions for patients who received a BED10 >= 100 Gy. Patients who were treated with SBRT who had <= 5 metastatic lesions at first recurrence had a superior 1 year OS of 100 vs 50% for those with > 5 lesions. One patient (6.3%) experienced a Grade 3 central nervous system toxicity. Conclusion: LC was excellent with SBRT delivered to metastatic disease, particularly for lesions receiving a BED10 >= 100 Gy. High -grade toxicity was rare in our patient population. Patients with five or fewer metastatic sites have a significantly better OS compared to > 5 sites. Advances in knowledge: This study demonstrates that SBRT is safe and efficacious in the treatment of pediatric oligometastatic disease.