Tumour DNA in the bloodstream can be used to predict the survival chances of patients with pancreatic cancer, research suggests.
The "liquid biopsy" could help doctors work out the best treatment strategies for patients with advanced forms of the disease, scientists believe.
Pancreatic cancer is one of the deadliest cancers because it is so often diagnosed late.
Scientists in the US looked for traces of circulating tumour DNA (ctDNA) in the blood of 135 pancreatic cancer patients.
Of these, 31 had operable tumours, 36 had locally advanced disease, and 68 had cancer that had spread around the body.
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Of the operable patients, six had detectable ctDNA. These patients survived for 19.3 months compared with 32.2 months for those with no tumour DNA in their blood.
Among the 104 patients with advanced disease, the 50 with detectable ctDNA survived just 6.5 months. The remainder with no ctDNA survived for 19 months.
Dr Jean-Baptiste Bachet, from Sorbonne University in Paris, said: "Our study ... confirms the strong prognostic value of the presence of ctDNA and of its level, when detected, in advanced pancreatic adenocarcinoma.
"Our results demonstrate the utility of circulating biomarkers in sub-classifying cancers and managing treatment.
"We need to confirm these results in prospective clinical trials to better assess the predictive value of this biomarker in light of the dynamic biological changes that occur during treatment."
The findings are published in the journal Clinical Cancer Research.
