DNA tests spot returning lung cancer a year before scans

Blood tests for tumour DNA could predict relapse of the most common type of lung cancer up to one year before clinical signs show up on patient's scans.

The new research, published in the journal Nature, presents the results of the first 100 patients with non-small cell lung cancer, recruited as part of a pioneering consortium called TRACERx. Led by Professor Charles Swanton at the Francis Crick Institute in London, this project aims to follow nearly 850 lung cancer patients from diagnosis through treatment and follow-up to examine how lung cancers evolve over time.

'We can now set up clinical trials to ask the fundamental question - if you treat people's disease when there's no evidence of cancer on a CT (computed tomograpy) scan, or a chest X-ray can we increase the cure rate?', Professor Swanton told the BBC.

Researchers took blood samples from each patient before surgery to remove their cancers, and every three months afterwards. These highly-sensitive 'liquid biopsies' detected any fragments of circulating tumour DNA (ctDNA) released into the bloodstream by dying cancerous cells. Samples from the removed tumours were also analysed to provide a genetic profile of each patient's cancer.

The vast majority of patients with a type of non-small cell lung cancer called squamous cell, 94 percent, had tumour DNA in their blood, while this was found in only 13 per cent of patients with another type of non-small cell lung cancer, adenocarcinoma. The study found that in almost all patients in whom the cancer returned, ctDNA increased in the blood months before the relapse and its DNA profile matched that of the returning tumour.

'This means that for the first time in lung cancer, we could open up clinical trials where patients with disease, that isn’t yet visible through medical imaging, can be treated with new drugs', said Professor Swanton to the BBC.

A limitation this targeted ctDNA profiling approach is cost, which the researchers estimate to be about $1750 per patient. However, the study explained that because of the fundamental tumour processes involved in producing ctDNA, the liquid biopsy method could apply to many other types of cancers.

Professor Swanton is now working with other scientists on the development of immunotherapies that could target novel biomarkers unveiled by ctDNA blood tests.