Treatment of infantile fibrosarcoma in the era of targeted therapies

Abstract

Infantile fibrosarcoma (IFS) is a very rare pediatric soft tissue sarcoma (STS). Resection with negative surgical margins without caus - ing morbidity is the mainstay of treatment. When primary surgery is not possible, satisfying results can be obtained with conventional chemotherapy and targeted therapy. We aimed to evaluate the demographic, clinical, laboratory and radiological characteristics and treatment outcomes of pediatric patients with IFS. We retrospectively reviewed medical records of the patients diagnosed with IFS 1990 and 2022. The mean age at diagnosis of 12 patients was 90 days. The most common tumor localization was extremity. None of the patients were metastatic at diagnosis. Primary surgical excision was performed in five patients;three of them had positive surgical margins and two of these patients experienced recurrence. Surgical margins were negative in other two patients who were operated on, and recurrence occurred in one of them. Of the seven patients treated with primary chemotherapy, two patients had complete response, surgery was not performed. Larotrectinib was initiated to three patients with NTRK fusions. At a median of 104-month (7- 206) follow-up, all patients are alive. Nine of the twelve patients survived disease-free for a median of 118 months (25-206). Although surgical resection is the mainstay of treatment of infantile fibrosarcoma, satisfying results can be obtained with chemotherapy and targeted therapy in inoperable cases. The use of targeted therapies can be increased by conducting molecular studies, especially in cases not suitable for surgery with a goal of avoiding side effects of conventional chemotherapy.