Update on pediatric soft tissue sarcomas

The purpose of this review is to highlight recent findings in the diagnosis, biology, risk-stratification, and treatment of soft tissue sarcomas (STS) in children.

In rhabdomyosarcoma (RMS), FOXO1 fusion status has been confirmed as an important prognostic factor. Among fusion-negative RMS, TP53 and MYOD1 mutations and detectable circulating tumor DNA at diagnosis are associated with inferior event-free survival in intermediate-risk disease. Delayed primary excision is associated with a reduced risk of local failure whereas radiotherapy dose escalation in large tumors has not improved local control. Maintenance therapy with vinorelbine and oral cyclophosphamide following induction chemotherapy in the RMS2005 trial led to improved survival. In non-rhabdomyosarcoma soft tissue sarcomas, the addition of pazopanib, a multitargeted receptor tyrosine kinase inhibitor, to upfront therapy did not improve survival. Atezolizumab is approved for alveolar soft part sarcoma, larotrectinib for NTRK fusion-positive STS, and afamitresgene autoleucel remains under evaluation in children with synovial sarcoma. Encouraging early results have been reported with tazemetostat and immune checkpoint inhibitors in epithelioid sarcoma and trastuzumab in desmoplastic small round cell tumor, respectively.

Pediatric STS are rare and biologically heterogeneous. Genomic advances have refined risk stratification and uncovered therapeutic targets; further progress relies on international collaboration and trials.