A revolutionary new cancer test
Nearly ten years ago a scientist at the world’s largest gene-sequencing business, Illumina, noticed an anomaly as she examined blood samples from pregnant mothers. In some samples the DNA of the unborn child was normal, whilst that of the mother was not.
The scientist, Meredith Halks Miller, suspected the changes in the maternal DNA samples were caused by cancer. On closer investigation, every single patient that Meredith predicted had cancer did turn out to have the disease.
The discovery led to the forming of GRAIL, a start-up business focussed on “liquid biopsies” – finding markers for cancer and other diseases from blood samples long before symptoms present. The business has just launched a simple test which can detect up to 50 cancers from a tiny sample of blood.
A ground-breaking new test
Sadly, many people who work in healthcare experience profound deja-vu when they read headlines about “pioneering”, “revolutionary” and “ground-breaking” new tests. If you scratch beneath the surface of lots of these stories, they frequently turn out to be far less than promised.
Google “Theranos” and you will reveal a saga running back years based on this very issue that is only now reaching its finale in Court.
But there is something quite special about GRAIL and a new test it has invented called “GALLERI”. Galleri analyses stray samples of DNA in a blood sample, to see if they indicate the presence of cancer.
Galleri has something else behind it too. It has what many new tests lack – decent evidence that it works.
The weight of evidence behind the test has led GRAIL to begin commercialising the test, even before they have full regulatory approval in the USA.
What can Galleri find?
An early version of the Galleri blood test has been under evaluation in the USA for some time. The results of the one large validation study have just been published.
The study, which involved 4,077 patients, showed that although the test had a 51.5% overall sensitivity (it missed just under half of all true positive cancers), it had a specificity of 99.5%. Nearly all those that it did find were accurate (“true positives”).
A test that misses nearly half of all cancers doesn’t sound great, however, the context is hugely important. The 51.5% pick-up rate was for Stage 1 cancers. The accuracy of the test increased markedly as the cancers advanced.
The sensitivity of the test when the cancers were between Stage 1 and Stage 3 was 68% – the test found two out of three cancers before they had progressed to Stage 4.
Early diagnosis saves lives
Many cancers, like pancreatic and oesophageal cancer, are incredibly difficult to diagnose at the earliest stages. Finding cancers at early stages significantly improves mortality – the quicker the cancer is found, the better the likely outcome. Nearly half of all cancers in the UK are diagnosed at later stages (Stage 4 or 5).
So a test that shows markers at an early stage, even if some are missed, really is ground-breaking.
On top of the ability to detect cancers at a very early stage, it also shows markers for up to 50 different types of cancer. A test that can find that many cancers, that early, really is quite remarkable.
Testing the test
Although the signs are incredibly promising, more data is needed to prove the impact the test has on patients over time.
Initial results of the UK study are expected by 2023 and, if successful, the NHS plans to extend the rollout to a further one million people in 2024 and 2025.
If the test does hold up to scrutiny in large trials, put quite simply, it will revolutionise cancer diagnosis worldwide.
The early signs are promising and it is also encouraging that the NHS is in the driving seat for the largest part of the international evaluation. The performance of the test will most likely be improved further over time too, which is also very positive.
Galleri may just be one test that is actually worthy of the name “revolutionary”. In a few years’ time we may be just as familiar with the name Meredith Halks Miller as we are with Louis Pasteur, Marie Curie and Joseph Lister.
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