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Blood test that finds 50 types of cancer is accurate enough to be rolled out

theguardian.com

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Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#251

Post by graeme »

plank_time wrote: post #137
jacquesm wrote: post #132

Earlier quoted context omitted.

Even if you detect cancer you will still need a biopsy to figure out which bits are the cancer and which bits are just 'lumps'. Yes, it is a game changer, but it is not the kind of game changer that this is being made out to be here and mass screening using this method is not going to lead to improved outcomes. As an extra tool in the toolbox of the diagnostician it is very useful.

It’s pretty easy. If blood test says “liver cancer positive. Colon cancer negative.” you check the liver for cancer. No need to check the colon for cancer. No need to scan the entire body for lumps.

Not that easy. “Check the liver for cancer” has lots of risks: surgery and the resulting tissue injury.

I’m generally inclined towards the position of more testing....but there are very real tradeoffs to any of the interventions that a blood test could prompt.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#252

Post by rackjack »

tnel77 wrote: post #244
rackjack wrote: post #223

Earlier quoted context omitted.

> Getting a cancer diagnosis today is a huge deal because testing is infrequent, usually in response to a problem, and the diagnosis tends to be late and accurate. Getting a cancer diagnosis is a "huge deal" because getting cancer is one of the worst experiences a human can go through. Getting cancer carries the weight of imminent death, obviously. But some cancers can be cured with high survival rate, so what's the…

>Getting a cancer diagnosis is a "huge deal" because getting cancer is one of the worst experiences a human can go through. I’ve never been given a cancer diagnosis, but I’d imagine it’s much, much worse to be told you have stage 4 cancer versus stage 1. As the other person stated, the culture would adapt and people would learn to not immediately sell their house and go on a Vegas bender just because a yearly prevent…

> I’ve never been given a cancer diagnosis, but I’d imagine it’s much, much worse to be told you have stage 4 cancer versus stage 1.

It's bad all the way.

> If you are one of the people with a false positive, you schedule a follow-up and move on accordingly.

People already do schedule follow-ups and additional tests and second opinions when they get a positive.

> Your position is anti-progress just for the sake of being against accidentally scaring a few people.

No, it is cautiously ethical because:

1. You probably shouldn't tell sub-1.5 million people who don't have cancer that they have cancer

2. There are more false positives than you think, if you are suggesting regular blood tests

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#253

Post by ggrrhh_ta »

dxyms wrote: post #134
ggrrhh_ta wrote: post #53

Earlier quoted context omitted.

Have heard your argument on the false positives and unnecessary interventions many times. It is not a good argument. In fact, it makes no sense. If you get a positive with an uncertainty in its accuracy, at the very least, the test is repeated. But even more, you can use the information from the investigation of the reason for the false positive to improve the tests in the first place. If we weren't humans and the un…

> If you get a positive with an uncertainty in its accuracy, at the very least, the test is repeated. But even more, you can use the information from the investigation of the reason for the false positive to improve the tests in the first place. This assumes that the false positive is caused randomly. That's not the case. False positive tests are usually followed by false positive tests. Then it will take years to fi…

That is very interesting. I assumed that false positives is generally a testing error (testing with another method or from another company would not lead to the same result). If the false positive is a result of a non-dangerous anomaly of the person being tested, then, I see how testing without symptoms can be worse.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#254

Post by iNane9000 »

TaupeRanger wrote: post #96
reacharavindh wrote: post #3

This is one of those medical revolutions that I am waiting dearly for. Facilities that are not hospitals(to avoid the risk of occupying medical devices that sick people need) built to _regulary_ check up otherwise healthy people for preventive care. Heck, I have so many alerts defined on my monitoring setup for servers to watch for signals of failure before they get too big. But, my own body is not observed until som…

Actually you don't want this, and you are describing a nightmare scenario that everyone who studies health policy understands all too well. Mass screening of healthy people will result in extreme iatrogenics and unnecessary psychological damage and stress (which leads to physical effects as well), not to mention overwhelming the medical system. The fact is that many things that could be detected will never result in…

As it stands wealthy people can and do find more thorough medical treatment, including more frequent and exhaustive imaging, labs, etc... The conventional wisdom you cite only applies to those who can’t seek endless second opinions from specialists. There are many conditions that exist and are treatable in wealthier societies. The poor suffer those same afflictions but are untreated or misdiagnosed.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#255

Post by rackjack »

avion23 wrote: post #242
rackjack wrote: post #190

Earlier quoted context omitted.

Same vibe as "I would just simply..." What do you think the entire medical, pharmaceutical, bioinformatic, etc. industries have been doing for decades? Are you really so arrogant to think that other people are too lazy and stupid to think of your brilliant idea and that you are simply more intelligent than everybody else? Do you really think people haven't been trying?

> Are you really so arrogant to think that other people are too lazy and stupid to think of your brilliant idea and that you are simply more intelligent than everybody else? Not OP, but yes, I do. I've had some runins with the health system. At least the parts that I've seen are worse than the dark ages. Especially endocrinologists have absolutely no clue what they are doing. The ones I met don't even have superficia…

You're talking about praxis, we're talking about research. I agree the praxis can be pretty bad, but in regards to the above commenter's remarks on why people don't just simply collect data and apply it, medical professionals simply cannot try out new treatments the way they are suggesting.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#256

Post by wgolsen »

bookofjoe wrote: post #248

What makes this even more revolutionary to me (retired anesthesiologist) is that the methodology allows for use of Theranos-style finger-prick-size blood samples rather than IV blood draw, since fragment identity is the indicator rather than level/concentration.

The concentration of cell free DNA in blood plasma is generally in the nanograms/mL range, meaning most cfDNA assays will require at least a ~mL of plasma input for sufficient sensitivity / reproducibility. We aren’t quite at the capillary blood level of sensitivity yet.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#257

Post by sdg56 »

rackjack wrote: post #184
plank_time wrote: post #147

Earlier quoted context omitted.

We don’t give colonoscopies to 20 years olds because it’s an expensive, invasive test with a low rate of cancer. We don’t give mammograms to under 40 year olds these days because the same and it’s notoriously inaccurate. We give blood glucose level tests and cholesterol tests to everyone every year at the physical because they are cheap and easy to administer. Even though the effects of both may take decades to have…

> 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. If all 300 million Americans get blood tested each year, that is 1 and a half MILLION people who are falsely told they have CANCER. One and a half MILLION people whose life gets turned upside down, WRONGLY, due to a blood test -- at least, until they take a second o…

They will not be told they have cancer. They will be told they probably should check something out. Everybody already knows they might have cancer, having a negative blood test would be a huge relief.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#258

Post by throwawaynotmd »

bryan0 wrote: post #245
throwawaynotmd wrote: post #109

Earlier quoted context omitted.

The argument you’re making has always bothered me because it’s hiding the ball. If finding something that otherwise carries no symptoms is best left untreated, then the fact that you found it should make no difference to the decision. The doctor should say that the best course of action is to do nothing. More information can never be harmful. If you know information is best not acted on in the abstract, then you also…

> More information can never be harmful. This is an extremely naive viewpoint and in some situations quite dangerous.

I should say, if you know ex ante that certain results are not worth acting on, then when you actually get those results ex post, you should ignore them just the same. So actually running a test cannot formally be the problem.

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#259

Post by AlexCoventry »

TaupeRanger wrote: post #96
reacharavindh wrote: post #3

This is one of those medical revolutions that I am waiting dearly for. Facilities that are not hospitals(to avoid the risk of occupying medical devices that sick people need) built to _regulary_ check up otherwise healthy people for preventive care. Heck, I have so many alerts defined on my monitoring setup for servers to watch for signals of failure before they get too big. But, my own body is not observed until som…

Actually you don't want this, and you are describing a nightmare scenario that everyone who studies health policy understands all too well. Mass screening of healthy people will result in extreme iatrogenics and unnecessary psychological damage and stress (which leads to physical effects as well), not to mention overwhelming the medical system. The fact is that many things that could be detected will never result in…

If we optimistically assume the claimed 0.5% false positive rate is accurate, and all of the US got tested annually, that's 1.64M false positives per year. Cancer.gov is telling me that approximately 1.8M USians were expected to get cancer last year. That's a positive predictive value of 52%. That still seems highly informative, to me; much higher than the PPV for mammography according to this (admittedly old) study: [1].

Assuming the 0.5% FP rate holds (again, I know that's optimistic), would you still regard universal testing with this method to be harmful?

[1] https://jamanetwork.com/journals/jama/article-abstract/40935...

Re: Blood test that finds 50 types of cancer is accurate enough to be rolled out

#260

Post by cromka »

elif wrote: post #180
londons_explore wrote: post #31

More technologies like this are coming... Is it worth taking blood samples now, keeping them in a freezer, and then waiting for the test tech to come so I can get it tested to see disease progression of whatever disease I get when I get older?

I take blood tests regularly. They are very picky about sample collection time.

Same thing with stool collection.
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