Stereotactic ablative radiotherapy extends time to subsequent systemic therapy in pediatric cancer patients with recurrent or metastatic disease

Abstract

Background and Aims

Stereotactic ablative radiotherapy (SAbR) has been used in the adult population for decades, providing local control (LC) and, in some cases, overall survival (OS) advantage. It can also extend the time to subsequent systemic therapy, reducing side effect burden and improving quality of life. This retrospective study aimed to evaluate the effectiveness of SAbR in prolonging time to subsequent systemic therapy in children.

Methods

We performed a single-institution retrospective analysis of children who underwent extracranial SAbR over 2 – 5 fractions (dose per fraction > 5 Gray [Gy]) for recurrent or progressive cancer between 2009 and 2024. The primary endpoint was time from SAbR to next use of systemic therapy. Secondary endpoints included LC and OS, as well as the impact of biological effective dose (BED) and equivalent dose in 2-Gy fractions (EQD2) thereon.

Results

Thirty-five pediatric patients with cancer had 97 lesions that received at least one course of SAbR meeting minimum dose criteria (BED10 ≥30 Gy). The cumulative incidence of any systemic therapy change at 12 months was 0.58 (95% CI 0.47–0.68). The cumulative incidence of IV systemic therapy change at 12 months was 0.36 (95% CI 0.26–0.47), with a median time to IV systemic therapy change of 11.9 months. Risk of local progression was associated with non-sarcoma histology compared with soft tissue sarcoma (Hazard Ratio [HR] 4.19; 95% Confidence Interval [CI] 1.25–14.06; p = 0.021). Median OS from first SAbR was 12.8 months (95% CI 7.82–26.20). There was no statistically significant association of LC with BED or EQD2.

Conclusions

In this single-institution case series, SAbR was associated with a delay to subsequent IV systemic therapy change in pediatric cancer patients and may serve as a means to manage disease progression while minimizing burden of therapy. Prospective studies are needed to confirm these findings.