In a major lung cancer trial, a revolutionary blood test has been proven to diagnose the recurrence of cancer cells up to a whole year in advance of conventional scans.
This test, known as a liquid biopsy, could buy some crucial time for doctors by indicating that cancerous cells are present in the body when tumors are detectable on CT scans and long before the patient has any physical symptoms.
The test works by detecting free-floating mutated DNA, which has been released into the bloodstream by dying cancer cells. In the lung cancer trial, which involved 100 patients, scientists saw precipitous rises in tumor DNA in the blood of patients who relapses months, or even a whole year, later.
These findings add to the building anticipation that this technology, which is also being used to test for Down syndrome, will lead to a major breakthrough in cancer medicine.
Nitzan Rosenfield, from Cancer Research UK Cambridge Institute, who was not involved in this latest trial, has predicted that “most if not all” cancer patients will be given this test in future. He goes on to say that “even if only a fraction of cancers that are currently detected at a lethal stage will in future be detected at an early curable stage this will represent a great benefit in lives saved.”
In the latest clinical trial, 100 patients with non-small cell lung cancer were observed from diagnosis through to surgery and chemotherapy, with blood tests being taken every 6-8 weeks. By analyzing the genetic faults in cells across each tumor, the scientists created personalized genomic templates for every patient. This was then compared to the DNA floating in their blood, to see whether a fraction of it matched that of their tumor.
Professor Charlie Swanton, a cancer geneticist from the Francis Crick Institute, who led the work, explained how circulating tumor DNA tracked the patient’s disease status with extreme precision. Of patients who would stay in remission, he declared that “within 48 hours of surgery, the DNA drops down to undetectable.”
By contrast, rising tumor DNA levels were seen in patients whose disease would later return, indicating that that the cancer remained in the lung or had moved to other organs, where it was dormant.
When the tests from 24 patients were analyzed, the scientists could say with 92% accuracy who would relapse.
Swanton goes on to declare that he thinks “this is going to be very useful clinically as this allows us to identify high risk patients. We have a predictive value of 92% that your cancer is going to recur within 350 days.”
The tests even went on to reveal an apparent outlier, a patient whose cancer had not returned, but whose blood tests revealed high levels of circulating tumor DNA, had the cancer return almost a year later.
The liquid biopsies also showed whether the chemotherapy treatment was working or if the disease had become resistant, as is what happens in the majority of stage 2 and 3 cancers. In future, this could allow doctors to switch to a more effective drug and spare patients grueling treatment for nothing.
Eileen Rapley, 74, a retired art teacher from London, entered the trial after being diagnosed with lung cancer over a year ago. Since she began her treatment, doctors have discovered that she has developed a brain tumor, for which she is also being treated. Although the liquid biopsy did not guide her own care, she hopes that this new test might lead to the kind of improvements that screening techniques have brought about for breast cancer.
The test used in the study relied on building a genetic template for each patient based on analysis of tumor samples, with an estimated cost of around $1,700. However, Swanton predicts that the same kind of profile could be built using computational methods from just an initial blood test, making the technology viable outside a research setting.
Lung cancer causes more than 1 in 5 cancer deaths in the UK and, although occurrence of the disease is falling, survival has only improved by a fraction in the last 40 years. Professor Karen Vousden, chief scientist at Cancer Research UK, which funded this study, said: “These findings could help us to identify how lung cancers respond to therapy, building a bigger picture of the disease and potentially pointing the way to developing new treatments and, crucially, saving more lives.”