Nurse, the screens...

There aint half been some clever bastards.
Post science, nature, technology and all geek stuff here.
Post Reply
User avatar
Gob
Posts: 33642
Joined: Tue Apr 06, 2010 8:40 am

Nurse, the screens...

Post by Gob »

A simple blood test that can detect more than 50 types of cancer before any clinical signs or symptoms of the disease emerge in a person is accurate enough to be rolled out as a screening test, according to scientists.

The test, which is also being piloted by NHS England in the autumn, is aimed at people at higher risk of the disease including patients aged 50 or older.

It is able to identify many types of the disease that are difficult to diagnose in the early stages such as head and neck, ovarian, pancreatic, oesophageal and some blood cancers.

Scientists said their findings, published in the journal Annals of Oncology, show that the test accurately detects cancer often before any signs or symptoms appear, while having a very low false positive rate.

The test, developed by US-based company Grail, looks for chemical changes in fragments of genetic code – cell-free DNA (cfDNA) – that leak from tumours into the bloodstream.

The Guardian first reported on the test last year and how it had been developed using a machine learning algorithm – a type of artificial intelligence. It works by examining the DNA that is shed by tumours and found circulating in the blood. More specifically, it focuses on chemical changes to this DNA, known as methylation patterns.

Now the latest study has revealed the test has an impressively high level of accuracy. Scientists analysed the performance of the test in 2,823 people with the disease and 1,254 people without.

It correctly identified when cancer was present in 51.5% of cases, across all stages of the disease, and wrongly detected cancer in only 0.5% of cases.

In solid tumours that do not have any screening options – such as oesophageal, liver and pancreatic cancers – the ability to generate a positive test result was twice as high (65.6%) as that for solid tumours that do have screening options such as breast, bowel, cervical and prostate cancers.

Meanwhile, the overall ability to generate a positive test result in cancers of the blood, such as lymphoma and myeloma, was 55.1%.

The test correctly also identified the tissue in which the cancer was located in the body in 88.7% of cases.

Dr Eric Klein, chairman of the Glickman Urological and Kidney Institute at Cleveland Clinic in the US and first author on the research, said: “Finding cancer early, when treatment is more likely to be successful, is one of the most significant opportunities we have to reduce the burden of cancer.

“These data suggest that, if used alongside existing screening tests, the multi-cancer detection test could have a profound impact on how cancer is detected and, ultimately, on public health.”

Dr Marco Gerlinger, from the Institute of Cancer Research in London and consultant medical oncologist at the Royal Marsden NHS foundation trust, said: “This new study shows impressive results for a simple blood test that can detect multiple cancer types.

“False positives are low which is important as this will avoid misdiagnoses. For some of the most common tumour types such as bowel or lung cancer, the test even picked up cancers that were very small, at a stage where many of them could potentially be cured.

“The study was done in patients whose cancer was already diagnosed based on other tests and this screening technology still needs to be tested in actual screening trials before routine use.

“But it already allows a glance at early cancer detection in the future which will almost certainly be built around liquid biopsy tests, which detect cancer DNA in the bloodstream.”

Meanwhile, the results of the NHS pilot of the test, which will include 140,000 participants, are expected by 2023.

Prof Peter Johnson, national NHS clinical director for cancer, said: “This latest study provides further evidence that blood tests like this could help the NHS meet its ambitious target of finding three-quarters of cancers at an early stage, when they have the highest chance of cure.

“The data is encouraging and we are working with Grail on studies to see how this test will perform in clinics across the NHS, which will be starting very soon.”
“If you trust in yourself, and believe in your dreams, and follow your star. . . you'll still get beaten by people who spent their time working hard and learning things and weren't so lazy.”

ex-khobar Andy
Posts: 5418
Joined: Sat Dec 19, 2015 4:16 am
Location: Louisville KY as of July 2018

Re: Nurse, the screens...

Post by ex-khobar Andy »

So false positives were 0.5% (good) but false negatives were close to 50% (not good)?

"The data is encouraging." I'd go along with that. But a negative result has to be taken with a very large pinch of salt (or Marmite if you prefer and you don't mind cross-threading).

User avatar
Scooter
Posts: 16540
Joined: Thu Apr 15, 2010 6:04 pm
Location: Toronto, ON

Re: Nurse, the screens...

Post by Scooter »

And that's across all stages of cancer. You'd have to assume that it's pretty shitty at detecting early stage cancers (which is where it would be of most use).
"If you don't have a seat at the table, you're on the menu."

-- Author unknown

ex-khobar Andy
Posts: 5418
Joined: Sat Dec 19, 2015 4:16 am
Location: Louisville KY as of July 2018

Re: Nurse, the screens...

Post by ex-khobar Andy »

I don't know the details of the test of course; but for most diagnostic tests there is a tradeoff. I would accept a much higher false positive rate if it helped to reduce the false negative rate. My reasoning is this.

In theory, the worst thing that can happen from a false positive is that someone gets a treatment they do not need. But in practice, any positive result, false or not, wold be followed up by further testing. They are not going to pull out or irradiate a piece of lung / colon / breast / whatever purely on the basis of a yes/no diagnostic test. There will be tests to locate exactly that piece of malignant tissue and at that point the initial result will be confirmed or refuted.

A negative result (false or not) will be followed by - good news, you're clear. See you again next year.

That why I say it is encouraging. But there's a way to go before it might be a game changer.

User avatar
Long Run
Posts: 6717
Joined: Sat Apr 17, 2010 2:47 pm

Re: Nurse, the screens...

Post by Long Run »

Seems to me if it can detect over 50% of cancers before there are any other symptoms, then it is doing a lot of good as people will get treatment a little or a lot sooner than they otherwise would have.

Burning Petard
Posts: 4048
Joined: Fri Feb 12, 2016 5:35 pm
Location: Near Bear, Delaware

Re: Nurse, the screens...

Post by Burning Petard »

This is touted as a SCREENING test. it should be biased to produce false positives, that will be checked by other procedures. False negatives mean some people with a problem will receive no further attention--wrong things falling through the screen.

snailgate.

User avatar
Long Run
Posts: 6717
Joined: Sat Apr 17, 2010 2:47 pm

Re: Nurse, the screens...

Post by Long Run »

Burning Petard wrote:
Sat Jun 26, 2021 10:33 pm
False negatives mean some people with a problem will receive no further attention--wrong things falling through the screen.
This misses the point entirely.

ex-khobar Andy
Posts: 5418
Joined: Sat Dec 19, 2015 4:16 am
Location: Louisville KY as of July 2018

Re: Nurse, the screens...

Post by ex-khobar Andy »

Long Run wrote:
Sun Jun 27, 2021 9:09 pm
Burning Petard wrote:
Sat Jun 26, 2021 10:33 pm
False negatives mean some people with a problem will receive no further attention--wrong things falling through the screen.
This misses the point entirely.

No, that's exactly the point. I agree that the test may be better than nothing and have some utility: but a screening test for cancer should always be biased to false positives, because that way it is much more protective of pubic health.

Big RR
Posts: 14048
Joined: Thu Apr 15, 2010 9:47 pm

Re: Nurse, the screens...

Post by Big RR »

With the proper use of the results, this screen could be quite helpful to some. If someone were to test positive, with a low false positive rate, it is quite likely the person has a particular cancer and treatment could be initiated right away. A negative test would/should be red as equivocal and not be relied upon. There area many tests clinical tests which are like this. I recall the Lyme disease (a number of years back, I don't know now) test had a fairly high false negative test, so testing negative was generally disregarded, while a positive test was seen as good evidence of having the disease.

Post Reply