Getting the right sarcoma diagnosis early is key to ensure patients receive the best treatment, but with so many subtypes, this can be challenging.
Prof David Gonzalez de Castro at Queen’s University Belfast turned to DNA circulating in the bloodstream to design an innovative diagnostic tool for some types of soft tissue sarcoma.
The idea
About a third of all soft tissue sarcomas are characterised by fusion genes, occurring when two “normal” genes are re-arranged together. Techniques to detect these unusual genes are now an integral part of the clinical diagnosis for many cancers, by taking a tissue sample and carrying out analysis to spot certain fusion genes. But this technique isn’t always effective in practice, as the sample of tissue obtained for diagnosing the cancer is often too small.
Designing a new blood test for sarcoma
Professor David Gonzalez de Castro and the team aimed to create technology that could identify 95% of all known fusion genes in blood samples – not just tissue samples. To do this, they utilised circulating tumour DNA (ctDNA), which is DNA circulating in the bloodstream, from patients with different types of soft tissue sarcoma.
The team developed a targeted panel test using technology called next generation sequencing, which analyses lots of specific genes of interest. The panel test was able to accurately detect fusion genes in 90% of tissue samples, and 50% of blood samples. This means that the test could identify genes that could help identify a particular sarcoma subtype – especially where a tissue sample might be unavailable for analysis.
This is the first time this type of test has been designed to detect ctDNA specifically for sarcoma. The tool was tested in over 100 samples, on a par with tests already on the NHS for some cancers.
What’s next?
Although there’s a way to go before we may see liquid biopsies like this used in a clinical setting for sarcoma, these results provide some proof of concept, which is exciting. Diagnostic tests looking for DNA in the blood are increasingly used in many types of cancer, such as the Galleri blood test. ctDNA is also used already to monitor more common cancers such as colorectal, lung and breast cancers.
Prof Gonzalez de Castro hopes that the results from this study could improve the diagnosis and treatment of sarcomas in the longer term.
Our research produced a clinical validation of a novel tool for the diagnosis of fusion-positive sarcomas (one third of all soft tissue sarcomas) and it was the first comprehensive tool to be used in circulating tumour DNA analysis, opening possibilities for earlier and non-invasive diagnosis and treatment monitoring. – Prof Gonzalez de Castro
