Synovial sarcoma in children: A 15-YEAR experience at a tertiary pediatric center in Argentina

Background Synovial sarcoma (SS) is characterized by local invasiveness and a propensity to develop distant metastases. Current treatment for pediatric patients is based on the strategy used by the two main international groups, the Children's Oncology Group (COG) and the European group (EpSSG). Overall survival (OS) and event free survival (EFS) vary according to different publications; however, they tend to be dismal in initially metastatic patients, as well as relapsed patients. Objective To describe the clinical, histopathological, molecular findings and outcome in a series of 22 pediatric patients treated at our institution over 15 years. Materials and methods A retrospective, descriptive study in patients with a histopathological or molecular diagnosis of SS between December 2005 and August 2019, treated according to the EpSSGNRSTS 2005 protocol. Results Median age at diagnosis was 138.1 months, 32.1% presented with a primary axial site, and 68% with a tumor larger than 5 cm. Initial metastatic disease was seen in 22.7%. Of initially localized patients, 70.6% were classified as high-risk. Chemotherapy was administered to 91% of our patients and 77.2% received radiotherapy. The 3-5- and 10-year OS and EFS was 66%, 58.7% and 48.9%, and 57%, 33%, 22.2% respectively. Localized patients had a 5- and 10-year OS of 73.3% and 61.1%, versus 40% and 0% in metastatic disease, respectively. The only statistically significant factors were presence of metastasis, tumor size and IRS group. Tumor relapse was seen in 31.8% of patients. Only patients with local recurrence that achieved a complete surgery are alive without disease. Treatment schemes after recurrence or progression included a combination of gemcitabine-docetaxel, vincristine-irinotecan-temozolomide, kinase tyrosine inhibitors, and metronomic therapy with cyclophosphamide or etoposide. A long progression free survival of 14 months was observed with etoposide. Conclusions Although the sample size was not large enough to draw robust conclusions, in our series, OS and EFS rates were found to be lower than those reported in other studies, probably related to unfavorable prognostic factors, including a high incidence of metastasis and tumors larger than 5 cm. New therapeutic strategies are needed to improve outcome, especially in metastatic and relapsed disease. In addition, assessing the role of maintenance therapy in larger numbers of patients and broadening the use of metronomic chemotherapy would be necessary.