A new blood test may be able to detect metatstatic melanoma relapse earlier than is currently possible, according to a study published in the journal Cancer Discovery.

Scientists from the Cancer Research UK Manchester Institute studied circulating tumor DNA in blood samples from seven advanced melanoma patients at The Christie NHS Foundation Trust.

They found they could see whether a patient was relapsing by tracking levels of circulating tumor DNA, and that new mutations in genes like NRAS and PI3K appeared, possibly causing the relapse by allowing the tumor to become resistant to treatment.

Around 40 to 50 percent of melanoma patients have a faulty BRAF gene and they can be treated with the targeted drugs vemurafenib or dabrafenib. But for many of these patients the treatments don't work, or their tumors develop resistance after a relatively short time. When this happens these patients can be offered immunotherapy drugs including pembrolizumab, nivolumab and ipilimumab.

"Being able to spot the first signs of relapse, so we can rapidly decide the best treatment strategy, is an important area for research,” says Professor Richard Marais, lead author and Cancer Research UK's skin cancer expert, in a news release. ”Using our technique we hope that one day we will be able to spot when a patient's disease is coming back at the earliest point and start treatment against this much sooner, hopefully giving patients more time with their loved ones. Our work has identified a way for us to do this but we still need to test the approach in further clinical trials before it reaches patients in the clinic."