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A new blood test that could ‘help detect eight common cancers before they spread’ is big news today.
There’s lots of excitement around the study behind the headlines, published in Science. And rightly so. It marks an important next step for scientists working on blood tests for cancer.
But some important details were skipped over in the discussion in the news.
The first thing to know is that this experimental test is a long way off being used to diagnose cancer. As some experts have said, it’s “promising but with several caveats and a significant amount of further research is needed”.
And that’s because using a blood test to confirm that people with cancer have cancer is very different to using that same test to detect the earliest hints of cancer in otherwise healthy people.
What’s exciting about a cancer blood test?
Finding an accurate blood test for cancer is the ‘Holy Grail’ for many researchers. Taking blood is a lot quicker, cheaper and less invasive than some other tests.
Cancer cells are different to normal cells in many ways – they have changes in their DNA and make different molecules. And in some cases, cancer cells shed these fragments of errant DNA and faulty molecules into a patient’s bloodstream, theoretically leaving them floating for detection by a blood test.
But so far, finding the right chunks of DNA or molecules to look for has proven tricky. It’s hard to find a marker that is sensitive enough – meaning it finds cancer every time – and specific enough – meaning it doesn’t ‘find’ cancer when it’s not there.
Developing a test that worked would mean patients could be diagnosed quickly, potentially sparing them anxiety when they don’t have cancer and speeding up treatment when they do have cancer.
And it could help find cancers earlier when they’re likely to be easier to treat.
So while this research is an important step in the right direction, it’s not yet the finished article.
As Professor Paul Pharoah, a cancer expert at the University of Cambridge, said: “it remains a promising, but yet to be proven technology.”
A cancer blood test is in the news. Here’s what you need to know: https://t.co/5NG4E3VBCb pic.twitter.com/hTMvSjA7dx
— Cancer Research UK (@CR_UK) January 19, 2018
What did the research find?
The study, from researchers at Johns Hopkins in the US, shows how their blood test can confirm the presence of 8 types of cancer (ovarian, liver, stomach, pancreatic, oesophageal, bowel, lung, and breast) in people already diagnosed.
Their test looks for faulty DNA and molecules from cancer cells that find their way into the blood. And they tested it on 1,005 patients who they already knew had cancer.
This is a key point. They were looking for cancer in patients who had already been diagnosed with cancer. To truly match the promise of a blood test for screening, as some news reports suggested this might be, the test would have to work in people who haven’t yet been diagnosed.
Across the 8 cancers the tests picked up cancer in an average of 70 in 100 cases. This is a measure of the test’s sensitivity. And that’s not bad for an experimental test.
But there was huge variation in sensitivity across the different types of cancer – it found 98 in 100 ovarian cancers, but only 33 in 100 breast cancers.
Interestingly, the test could also tell the researchers the organ or tissue where the cancer came from in 83 in 100 patients. This would be incredibly useful for doctors if this type of test were to one day be used to diagnose cancer.
Finding cancer when it’s there is one piece of the puzzle. Another is making sure you don’t ‘find’ it when it isn’t there – known as false positives.
So the US team ran the test on 812 healthy people. It came up positive in 7 of these people, which, for a test at this stage of development, is a pretty low false positive rate of around 1% and definitely a good sign for the specificity of this test.
What is the research missing?
Cancers are split into different stages – the lower the stage, the earlier the cancer. This means it’s likely to be smaller, hasn’t spread and is probably going to be easier to treat. Any test with the goal of being able to detect cancers at the earliest stages in healthy people must strike the right balance between sensitivity and specificity.
“The sensitivity of the [blood] test in stage I cancer is quite low, about 40%, and even with stage 1 and 2 combined it appears to be around 60%,” said Dr Mangesh Thorat, a cancer expert at Queen Mary University of London. “So the test will still miss a large proportion of cancers at the stage where we want to diagnose them.”
This is really important for a successful test – the earlier it can pick up cancer the better. If it’s only good at finding later stage cancers, these are harder to treat.
Also, the proportion of common cancers detected (such as breast, lung or bowel) isn’t as high as with other, rarer cancers included in the study.
“This may mean that a screening programme has to test a very large number of individuals to detect one cancer,” said Thorat.
This increases the chance of false positives, potentially causing anxiety and further unnecessary testing.
Professor Nicholas Turner, a cancer blood test expert at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, said the 1% false positive could be a concern if a test like this were to be used to screen everyone, including healthy people.
“There could be a lot of people who are told they have cancer, who may not have it,” he said. “We can only learn about how much this is, or is not, a problem through larger studies. Much larger studies will also be needed to address whether using these blood tests can help improve survival rates.”
Any new test also needs to be better than the ones we have already. For example, with bowel cancer, there is already an effective screening programme to help detect the disease at an early stage. It can also prevent bowel cancer developing in the first place.
And while the experimental blood test in today’s news looks like it does a good job of predicting where a cancer is growing, in about a quarter of cases it may not be able to do so.
“Lots of imaging may be required to further diagnose the cancer, and we may still fail to identify the site, which creates an issue of what to tell these otherwise healthy individuals,” said Thorat.
What should you take away from this?
This is really important research, deserving of bigger studies. We need to do more research like this.
Dr Richard Marais, director of the Cancer Research UK Manchester Institute, said: “Hopefully in the future we can develop a blood test such as this that can be used routinely in patients, perhaps once a year, to allow them to know earlier if they have cancer and to get them treated much sooner.”
But as Turner added: “The study does not support use of the blood test outside research studies, as it has not shown yet whether the blood test has the characteristics required for population screening.”
With further research, the hunt for this scientific ‘Holy Grail’ will continue. And larger studies will test these tests under the right conditions to know for sure if it can be used to detect cancers earlier.
Cohen, J.D., et al. (2018) Detection and localization of surgically resectable cancers with a multi-analyte blood test. Science
Ms Hummel Charmen February 5, 2018
Incredible interesting. In the UK early discovery of cancer in patient is very much lower than in other developed countries. Why is this. I have CLL and had Lymphoma (in remission). I do not believe Doctors have sufficient time with their patients to truly analysis if a patient has possible cancer, even those with a history and that must change. My own story has been of missed diagnosis and misdiagnosis until it was almost too late for me. I am still suffering from the Chemo and the damaged the late diagnosed Lymphoma in the spine. Everyday I live in fear of a reoccurring cancer
Tracey Lunn February 5, 2018
I think thesa tests have already been done. And I think this “so called new test” is just to quieten people
Lorraine foster February 5, 2018
I think it would be a very good idea would help save a few more lives I have lost friends and family to this cruel desease
Lorraine February 5, 2018
mmm. I do wish the ‘media’ would be more circumspect with its headlines.
this is a very exciting start of potentially an amazing step forward in diagnosing many cancers, thank you for the thoughtful, informative report.
Lorna McCallum February 4, 2018
Is it only 4th Feb this test available
Trevor evans February 4, 2018
Anything that provides more information on cancer and how to tackle it is a GOOD THING
Tom February 4, 2018
Big target area 1in2, big return
Diane Laverne Inns February 4, 2018
Great news. Too many people woth cancer nowadays.
Sally Mamos February 4, 2018
I think it’s really important to carry on this research and put it into practice ASAP
Christina Yates February 4, 2018
I had breast cancer in September 1989 when I was 42. I had a mastectomy and my lymph glands were clear but my breast was full of cancer cells. I hadn’t had a mammogram prior to my op on 2nd Nov. I had to wait till late January by which time I was almost a basket case!! I had gone back to work far too early because I couldn’t stand waiting at home as my surgeon seemed convinced my right breast would also be full of cancer, I actually lost 10 years when the head radiographer told me I was clear, phew, I can’t forget the relief I felt. I’m 70 now and keep hoping that it won’t return to get me!!
Are aretha De Ste Croix February 4, 2018
I understand everything you have stated above but what about initially using the blood test on those individuals whose family history show a very high incident of some cancers. You mention that it could state a person has cancer who has not, but that would allow for further investigation, which, if your family’s cancer stats were as high of mine would more than acceptable
Lawry Ross February 3, 2018
These articles about research results which have made the news are so helpful because they put the research in context and fill in the gaps left by the headlines. Thank you so much for publishing them, they are authoritative and put everything in perspective.
Ruth Beresford February 3, 2018
Well, I hope they will improve their time for results. My sister had a genetics blood test st last Sept due to a diagnosis of breast cancer (myself & our Mum also have had it). had to wait 10 weeks for a result which didn’t arrive as the bloods were lost. More taken which took 12 weeks to come back. By this time she was booked in for her op so not time to change her procedure. Disgraceful.
Yvonne Murphy February 3, 2018
Most people have been affected by cancer in some way. I would definitely give blood for this life changing research.
kath Lawton February 3, 2018
This sounds absolutely amazing, It is a great step forward and would save many many lives, I hope that it can be used and if so, as soon as possible.
Callum Satchel February 2, 2018
Does not test for Prostate Cancer, which is in the news today..
Donald Lunn February 2, 2018
Twice I have posted a comment that I would be happy to take part in clinical trials.Twice it has not been posted.This is the third and last time.
Donald Lunn February 2, 2018
Any advancement is great news.What could we do to provide more research.If everyone upped their donation on a monthly basis.Would this Be Of any help.And what of “Big Pharma” Of Which we hear increasingly more of.Will they intervene.Because as we all know.Cancer treatment is a big money earner for these pharmecutical businesses.I would willingly increase my donation.”IF” and its a big If.It goes to the right organisation.
Tracey Turner February 2, 2018
I was offered a blood test as I gave breast cancer in my family, I never took up the offer at the time after a scare. Can I still have the test done, .. I believe this is a step in the right direction for cancer research UK.
ronnie burt February 2, 2018
any research that helps to gain more knowledge regarding early diagnosis is surley a wonderful step forward
Elaine Reed February 2, 2018
Sounds a great idea, having had breast cancer I always live in fear I might get cancer again and just having a mamagram once every 3 years I feel is not enough.
Theodore Oliver January 31, 2018
Of the few ‘false positives” in the cancer-free test patients at Johns Hopkins, is a check being run on any of them to see if a cancer develops in time which might indicate an early warning did in fact occur?
Michael Walsh February 1, 2018
That’s a really good question and unfortunately we don’t know. It’s definitely something that would need to be done when trialling any test that was going to be used to diagnose people.
Cancer Research UK
Elaine Storey January 20, 2018
Diagnosis of cancer has a devastating effect on your life & that of loved ones. Any step in the right direction is welcomed. Continue to support research to rid the world of this terrible disease!
Julie Whalley January 20, 2018
It’s hopefully a step in the right direction & hopefully more progress will be made with further research to increase the accuracy. Cancer is a bad disease & I live in hope that mine doesn’t return
Annabel A January 20, 2018
I had every blood test known to man and was told I had nothing nasty going on inside my body as they all came back normal. A month later doctors incidentally found two tumours on my thyroid?? I then had to go through numerous scans and needle biopsy’s, and two operations to have a final diagnosis of cancer. It would have been far less traumatic if the initial blood test had shown cancer.