CIRCUS: CIRCUlating tumour cells in soft tissue Sarcoma - a short report.

Aims: Circulating tumour cells (CTCs) can be detected in peripheral blood using their physical properties (increased size and less deformable than normal circulating blood cells) or using cell surface markers. The study of these CTCs should provide important insights into tumour biology, including mechanisms of drug resistance. We performed a pilot study (IRAS ID: 235459) to evaluate if CTCs could be isolated from peripheral blood samples collected from soft tissue sarcoma (STS) patients. Methods: We used a combined approach that first enriched samples for CTCs using a microfluidic cassette via Parosrtix^TMPR1, and then sorted cells stained for vimentin and cytokeratin using the DEPArray^TM. The total circulating cell-free DNA (cfDNA) level was also analysed. Data were correlated with clinical parameters. Results: 13 patients were recruited to this study: 7 patients with localised disease and 6 patients with metastatic disease. CTCs exhibited a high heterogeneity based on their expression of mesenchymal and epithelial markers. There was no significant difference in the number of CTCs between patients with localised versus metastatic disease. We observed no correlation between CTC numbers and cfDNA; however, the number of CTCs did correlate with primary tumour size. Conclusion: The present study demonstrates the presence of CTCs in STS patients with localised and advanced disease. Further and larger studies are needed to characterise STS CTCs and to evaluate their prognostic significance.