Even healthy people get cancer so the Galleri blood test could be a life saver for early detection.
A blood test that can detect cancer early has shown positive results. But like all NHS trials, access to the product can take years. Could the NHS push the envelope on this one?
The NHS has completed its trial of 140,000 volunteers who took the Galleri blood test, a test that claims to detect not all but up to 50 cancers. The trial was open to people registered with a GP in Cheshire and Merseyside, East of England (North) and Greater Manchester and aged 50 to 77. Participants could not take part if they had been diagnosed or treated for cancer in the last 3 years. The participants have been invited to take three appointments over two years, about 12 months apart, which means it could be years before the NHS greenlights the test so patients have access.
NHS National Director for Cancer, Professor Peter Johnson said the promising results of an early clinical trial into the Galleri blood test, were able to correctly identify two out of every three cancers among 5,000 people who had visited their GP with symptoms.
140,000 volunteers but only half of them got the Galleri test
However, only half of those who participated were given the blood test. When they joined the trial, a computer randomly put them in the test or control group. This was like the computer flipping a coin- you had a 50:50 chance of being in either group. Participants will not be told if they are in the test or the control group, not even after the trial has finished.
Most people on the trial will not get a test result. Only people in the test group who have a cancer signal detected will be given their test results. If some positive markers for cancer are detected after taking the blood test you will be out on a two-week waiting list for cancer referral to fast-track you to see cancer specialists.
People in the control group will have their blood samples stored. For anyone who was concerned about their health, this could add additional stress, but the risk must have been worth it.
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How does the Galleri cancer detection test work?
Every cell, including both healthy and cancerous ones, releases fragments of its DNA into the bloodstream, known as cell-free DNA. One of the defining characteristics of cancer is the addition of methyl groups to DNA.
Now you may be thinking what are methyl groups and how do they impact our DNA or lead to cancer?
Imagine your DNA as a set of instructions for your body. Methyl groups are like tiny chemical tags that can be attached to these instructions. Normally, these tags help control which instructions are used and when.
In healthy cells, these tags are added in a balanced way. This helps keep important genes “on” and harmful genes “off.”
However, in cancer cells, this tagging process can go wrong. Sometimes, too many or too few tags are added. This can have two main consequences:
- Silencing good genes: Important genes that normally help control cell growth and repair can be turned off by too many tags. This allows cancer cells to grow and divide uncontrollably.
- Activating bad genes: Genes that promote cancer cell growth can be accidentally turned on by the wrong tagging pattern.
This doesn’t change the underlying genetic code but can influence how genes are expressed. The methylation patterns found on cell-free DNA originating from tumours contain unique signals specific to cancer. These signals hold immense potential for detecting cancer and pinpointing its source.
Galleri, the company behind the cancer-detecting blood test, leverages next-generation sequencing technology and machine learning algorithms to analyse these methylation patterns within cell-free DNA present in the bloodstream.
NHS Galleri trial
If you would like to learn more about the Galleri NHS study click here.