Cancer care will be revolutionised by blood tests that can detect relapses within days and spot tumours in healthy people up to a decade before the first symptoms appear, scientists have said.
The tests can find growths while they are still as small as a pinhead during annual NHS check-ups for high-risk groups such as smokers, the over-50s or people with a family history of cancer. This would allow surgeons to operate early on the patient.
Some researchers claim that the screening tests could cut the number of cancer deaths by as much as 40 per cent in the near term, rising to 90 per cent if the devices reach maximum sensitivity.
The tests, which are known as liquid biopsies and flag up tiny fragments of tumour DNA that leak into the bloodstream as cancer cells die, could become a part of routine health checks within five years, according to one academic. Others believe that it will take longer to overcome a host of technical challenges and say that for now the method is better suited to tracking the progress of cancers after treatment.
Bill Gates and Jeff Bezos are among the investors who have poured $100 million of funding into Grail, a Silicon Valley startup that has said it will bring a prototype to market in 2019. A Grail-funded study presented over the weekend at the American Society of Clinical Oncology (ASCO) annual conference showed that a new kind of liquid biopsy designed to minimise false alarms had found 89 per cent of tumours in patients with advanced lung, breast and prostate cancer.
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Another American company, Guardant Health, has announced a clinical trial that will aim to detect the first hints of cancer in thousands of patients known to have inherited genes that put them at risk of the disease.
Findings from a third study at the conference, led by the Melbourne University, indicated that a much simpler version of the test could pick up about 50 per cent of early pancreatic cancers by looking for a single mutation.
One of the big advantages that liquid biopsies may have over other screening tools for cancer is a much lower rate of false positives. Several studies suggest that fewer than 0.5 per cent of people would be given a wrong diagnosis by using the method. The main drawback is that the technology can pick up only 30 to 50 per cent of early-stage cancers at present.
Peter Gibbs, a senior bowel cancer researcher who worked on the Melbourne study, said he expected the first screening devices capable of detecting the most common kinds of tumour to be used by doctors within three to five years. The tests cost about £775 at present but that could soon come down to as little as £150. Dr Gibbs envisages all people over the age of 50 undergoing cancer screening once a year.
Bert Vogelstein, professor of oncology and pathology at Johns Hopkins University and one of the fathers of the liquid biopsy, said: “If you could detect all cancers while they are still localised, you could diminish cancer deaths by 90 per cent. But that’s a theoretical figure. The available data suggest that it’s going to take quite a while, and there are a lot of obstacles to overcome.”
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• A cancer app that tracks patients’ symptoms could extend their lives by about five months. Scientists at the Memorial Sloan Kettering cancer centre in New York found using smartphones to alert doctors to problems that patients might not think worth reporting had a stronger effect on life expectancy than some frontline drugs. Similar technology is being tested in the NHS.
Analysis
Anyone who follows health news could be forgiven a niggling twitch of déjà vu (Oliver Moody writes). Blood tests for prostate and ovarian cancers have shown great promise only to be abandoned by doctors.
Why should the liquid biopsy be any different? There are two answers. The first is the tendency to cry wolf. The CA 125 test, for example, wrongly tells 22 per cent of healthy women that they have ovarian cancer. However, there is evidence that liquid biopsies could deliver false positives significantly less than 1 per cent of the time.
The other reason to be hopeful is the versatility of this technology. Peter Gibbs, of Melbourne University, said that researchers were on the brink of a single DNA test that could identify 90 per cent of the most common cancers at an early stage. This alone could allow tens of thousands more patients a year to be cured while their tumours are small enough to cut out.
