Therapeutic strategies and clinical evolution of patients with infantile fibrosarcoma: a unique paediatric case series

Background: Infantile fibrosarcoma is the most frequent soft tissue sarcoma in newborns or children under one year of age. This tumour often implies high local aggressiveness and surgical morbidity. The large majority of these patients carry the ETV6-NTRK3 oncogenic fusion. Hence, the TRK inhibitor larotrectinib emerged as an efficacious and safe alternative to chemotherapy for NTRK fusion-positive and metastatic or unresectable tumours. However, real-world evidence is still required for updating soft-tissue sarcoma practice guidelines.

Objective: To report our experience with the use of larotrectinib in pediatric patients.

Methods: Our case series shows the clinical evolution of 8 patients with infantile fibrosarcoma under different treatments. All patients enrolled in this study received informed consent for any treatment.

Results: Three patients received larotrectinib in first line. No surgery was needed with larotrectinib, which led to the rapid and safe remission of tumours, even in unusual anatomical locations. No significant adverse effects were observed with larotrectinib.

Conclusion: Our case series supports that larotrectinib may be a therapeutic option for newborn and infant patients with infantile fibrosarcoma, especially in uncommon locations.