blood test for cancer

What Are GRAIL Blood Tests for Cancer?

In 2021 the NHS started the NHS-Galleri trail - a research trial to see how well the Galleri blood test would work in the NHS. Blood testing kits could help to find Cancer early and cheaply.

The aim is to see how well Galleri can help detect cancer early, alongside the UK’s cancer screening programmes. The objective is to try and detect cancer as early as possible when often people have no symptoms. Early detection and then early treatment are accepted as the most successful way to treat cancer.

What is Galleri?

Galleri is a Multi-Cancer Early Detection (MCED) blood test, manufactured by a company called GRAIL. Galleri works by detecting cell free DNA from tumours that are present in the blood. In essence what the test is looking for is DNA fragments in the bloods and their cancer specific signals. This is based on the understanding that some cancer tumours shed DNA into the blood a long time before symptoms start to show. Galleri checks more than 100,000 DNA regions and over a million specific DNA sites looking for cell free DNA. The Galleri test can detect more than 50 types of cancer. It is important to note that it doesn’t detect all cancers and experts are keen to point out that it should not replace regular cancer screenings. In fact the company is keen to point out that their hope is that the test will complement screening programmes, not replace them.

The NHS Trial

The trial, currently ongoing in the NHS, is a randomised control trial and requires volunteers to give a blood sample, then another 12 months later, then another 2 years after that. 140,000 volunteers have been recruited, aged between 50-77 from a range of different ethnicities and backgrounds. Volunteers also were not to have had a cancer diagnosis in the past three years. The Galleri trail is ongoing, but the hope is that future blood tests like this could be carried out at home.

The Symplify Study

The Symplify study was a collaboration between the University of Oxford and GRAIL. It was a nationwide study that began in the summer of 2021. Its 1st set of findings were published in June 2023.The Symplify study looked at the performance of a Multi Cancer Early Detection test (MCED) in people who had seen their GP for diagnostic follow up for suspected cancer. 

The study involved 6,238 patients aged 18 and over who had seen their GP with symptoms that could be cancer. Patients had symptoms which included rectal bleeding, weight loss and anaemia. Participants provided a blood sample which was tested for cell free DNA and results were then compared with the diagnosis obtained through the standard route.

GRAILS MCED test detected a cancer signal in 323 people, 244 in whom cancer was diagnosed giving a positive predictive value of 75.5%. The overall accuracy of the top cancer signal origin (CSO) prediction after a positive test was 85,2%. This has given hope to the opportunity to use this test to help doctors particularly in non-specific symptomatic situations. The accuracy of the test was also dependent on the stage of the cancer ranging from 24% for very early tumours-stage 1, to 95% for more advanced cancers stage 1V. The most common cancer diagnosis were bowel (37%), lung (22%), uterine (8%), oesophago-gastric (6%) and ovarian (4%).

The excitement around this study, alongside the NHS/Galleri study, is that this test may pave the way to detect cancer early and therefore allow for early treatment, which could save thousands of lives each year.

Galleri Test in the US

The test is currently used in the US. It is available on prescription only and, depending on the State guidelines, this could be a doctor or nurse. The test is then sent to the individual who then has to take it either to a lab or to where the person who wrote the prescription is. Bloods are then taken and sent away for testing. All results are sent directly back to the person prescribing the test. Results will either read, ‘cancer signal not detected’ or ‘cancer signal detected’ and ‘top predicted cancer signal origin’, where the cancer is coming from. If the latter is the result, then the individual will be sent for further testing before a formal cancer diagnosis is made.

It is important to note what the test cannot do-it cannot detect all cancers, it does not replace screenings and it cannot predict your risk of developing cancer in the future.

To enable the test to be widely used in the US the test has gone through rigorous testing. Two results are interesting-the PATHFINDER and CCGA3 studies. PATHFINDER tested on 6,600 individuals aged 50-79. Using the test doubled the numbers of cancers detected and offered a very high accuracy of predicted cancer signal origin which thus enabled for targeted diagnostic evaluation to follow.

CCGA3 involved 4,000 participants and results were a low false-positive rate, high accuracy of CSO prediction and it detected cancer signals across a wide range of different cancers and a wide range of cancers at different stages of development.