Synovial sarcoma in children and adolescents: a critical reappraisal of staging investigations in relation to the rate of metastatic involvement at diagnosis.

Background: European protocols for paediatric synovial sarcoma (SS) require that all children routinely undergo chest computed tomography (CT) scanning and bone scanning as initial staging procedures. This study aims to determine the rate of initial metastases in paediatric SS based on specific clinical characteristics, thereby investigating whether these diagnostic procedures are really necessary in all patients.

Methods: Data on 258 previously-untreated SS patients <21 years old were pooled from the databases of different European paediatric groups (study period 1988-2005) for this analysis, and the associations between patients' characteristics and any presence of metastasis were estimated.

Results: Fifteen cases (5.8%) had distant metastases at diagnosis (86% pulmonary). The presence of metastases was unassociated with patients' gender or age, tumour grade or site, but it was influenced by T-status, and especially primary tumour size: the risk of metastases was 32 times higher in cases of tumour >5 cm than for tumours ≤ 5 cm.

Conclusions: Our findings suggest that tumour diameter can be used as a variable for identifying patients at greater risk of metastases and warranting more accurate radiological investigations. Chest CT scanning may improve the accuracy of pulmonary staging over X-ray, but requires different ionising radiation exposures that might have carcinogenic potential: it can be omitted for patients with tumours ≤ 5 cm. Given the very low risk of bone metastases, bone scans may be recommended only in cases with evidence of lung metastases.