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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

#181

Post by doctoring »

giantg2 wrote: post #171

If it's detecting 50 types of cancer and the patient doesn't have symptoms, do they just do a full body MRI to find the source? If so, why not just do full body scans which can find other issues, like aneurysms or the other almost 50% of positives that it missed? I get that cost is a big issue, but it seems like the test is missing a lot and you might get more bang for the buck with a periodic MRI from the perspectiv…

Hey, radiologist here.

So, the question of "what next" after a positive result on one of these tests is still... open. The Grail test provides indication of likely tissue of origin, so a likely first step may be a targeted study (e.g. colonoscopy if it said a colonic source, MRI if it said pancreatic). There may be role for PET/CT as well to further stage and assess for metastases, perhaps after finding a lesion.

What to do if your blood test is positive but the workup is negative? Lots of discussion but nobody is quite sure.

As for a periodic full body MRI, I will say that currently uh, most of those are garbage. Unfortunately, for a full body MRI to be practical (that is, to not take hours and hours), you have to run very few sequences. (For example, a dedicated MRI of say, your brain or your liver alone could take about hour, each.) As a result, you greatly reduce your sensitivity for most pathologies, which kind of is counter to the point of the MRI to begin with.

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

#182

Post by fallingknife »

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…

I think it has more to do with how the kind of data collected from those mass screenings could be used to build predictive disease models that would put a lot of the guys making >= $300K to do a very poor job of keeping people healthy out of business.

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

#183

Post by Silhouette »

jacquesm wrote: post #123
amluto wrote: post #112

Earlier quoted context omitted.

You’re making an unwarranted assumption: that the choice is between early detection with current responses to detected cancers and no early detection at all. Optimizing the response to an early detection will give a result no worse than either of those, since the choices of what to do include doing whatever doctors did in the studies that have poor results as well as doing nothing at all.

No, that is not the assumption. The assumption is that the only way in which such a test will be useful is by applying it absent symptoms to the population en-masse aka screening. And that - no matter who good the test, and no matter how early - leads to a decrease in positive patient outcomes. This is established medical science, and it pains me to have to continue to point out the same thing over and over again, bu…

And that - no matter who good the test, and no matter how early - leads to a decrease in positive patient outcomes.

You keep writing comments in absolute terms and talking about evidence, but how do you reconcile your position with the results of successful screening programmes like cervical smear testing? Detecting and treating high risk HPV before it causes changes that can turn into cervical cancer has dramatically reduced the harm caused by cervical cancer itself at a population level. Routine screening of this type isn't normally recommended for young women, but it becomes increasingly effective with age and screening programmes operate accordingly.

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

#184

Post by rackjack »

plank_time wrote: post #147
TaupeRanger wrote: post #138

Earlier quoted context omitted.

You say "utterly wrong" and yet you clearly have no idea what you're talking about and have never even approached the field of health policy. Screening has to PROVE that it makes people live longer or better, just like any other intervention. It is not the case that screening is automatically good, otherwise we would be giving 20 year olds colonoscopies. Just because you find something, doesn't mean you've helped the…

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 one. Or a third one. Or maybe they get unlucky never learn they don't have cancer, and mess up their life treating a disease they don't have.

Now, OBVIOUSLY not all 300 million Americans are going to get tested each year. But you are completely ignoring the ethical concerns surrounding telling literally .5% of those who don't have cancer that they have cancer, and the non-insignificant proportion of people who will never learn they don't have cancer (we NEED to consider even the "miniscule" probabilities at this scale), and that makes you seem like somebody who "think[s] they know better".

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

#185

Post by dekhn »

jacquesm wrote: post #80
iandanforth wrote: post #76

Earlier quoted context omitted.

I detest this mindset. It is incredibly counter productive. "Our tests are bad, so lets not test" is not a thought worthy of respect. This states that you know about a problem but want to continue to ignore that problem. Reprehensible. No, we should take the exact opposite approach. Test everyone constantly until such methods become both cheap and powerful. So yeah we all have some cancer load but if the diagnostic o…

The problem is not my mindset, but your understanding of the subject material. Patient outcomes have very little to do with the quality of the tests, even a 100% accurate test would not necessarily lead to improved patient outcomes because these are defined independent of the tests. You are treating this like a software problem, but it isn't, it's a medical problem, and medical problems tend to be complex because the…

I think you should stop trying to derate people who you think know less than you. It's very unattractive. Be aware there are folks with extensive public health experience (that would be me) watching you insist you're right. While I totally appreciate what you're trying to do (help software engineers understand why medicine is complex), please do understand that GRAIL is tightly integrated with the PH community, did their work from a good-faith perspective, and came up with a product that does "do" something. Now it's up to the medical community to evaluate whether it truly provides something that doesn't just end up costing us more money and not helping people.

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

#186

Post by fallingknife »

TaupeRanger wrote: post #133
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…

Lots of problematic assumptions in your reply. >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. Absolutely and demonstratively false. There is an entire field of health policy that destroys this harmful…

> but doctors can't always predict this and aren't perfect decision making machines

So mass screen healthy people, collect the data, run models, and get better at it. People like you would rather not try, and this is the same reaction I get from doctors. Applying the same tech that we use to improve ad targeting to disease prediction is a no brainer to anyone whose cushy job doesn't depend on the current medieval state of medical technology.

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

#188

Post by laputan_machine »

pessimizer wrote: post #162
laputan_machine wrote: post #117

Earlier quoted context omitted.

You come in and flame other users, but then take deep offense when you get it back. Treat others with respect and in turn you'll receive it.

Disagreement is not "flaming." Jacquesm has been generally respectful and factual. The closest they have come to rudeness is when people refer to "facts" not in evidence or link to things that they haven't read or understood well, and even that impatience was explanatory. This comment is simply a personal attack.

I am sorry if you cannot understand what I am talking about, that you are clearly misunderstanding what I am saying.

I will write in this deeply arrogant fashion and refuse to link to anything I'm talking about, and when questioned I will infer that the people I'm replying to are utterly moronic (without saying quite such, I will instead say things like 'I'm sorry you don't understand / let me make this clear / you shouldn't be posting things you don't understand').

I will continue to write as if my stance is absolutely correct even though I am not an expert in this field, I will write as if I am.

And then when people call me out for my arrogance I will insist I've done nothing wrong and will be confused.

Baffling.

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

#189

Post by giantg2 »

doctoring wrote: post #181
giantg2 wrote: post #171

If it's detecting 50 types of cancer and the patient doesn't have symptoms, do they just do a full body MRI to find the source? If so, why not just do full body scans which can find other issues, like aneurysms or the other almost 50% of positives that it missed? I get that cost is a big issue, but it seems like the test is missing a lot and you might get more bang for the buck with a periodic MRI from the perspectiv…

Hey, radiologist here. So, the question of "what next" after a positive result on one of these tests is still... open. The Grail test provides indication of likely tissue of origin, so a likely first step may be a targeted study (e.g. colonoscopy if it said a colonic source, MRI if it said pancreatic). There may be role for PET/CT as well to further stage and assess for metastases, perhaps after finding a lesion. Wha…

Oh, so the test does give the source. I must have missed that part of the article thinking it was only identifying that there was a source in the cfDNA that was abnormal, but not realizing they could determine where it came from.

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

#190

Post by rackjack »

fallingknife wrote: post #186
TaupeRanger wrote: post #133

Earlier quoted context omitted.

Lots of problematic assumptions in your reply. >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. Absolutely and demonstratively false. There is an entire field of health policy that destroys this harmful…

> but doctors can't always predict this and aren't perfect decision making machines So mass screen healthy people, collect the data, run models, and get better at it. People like you would rather not try, and this is the same reaction I get from doctors. Applying the same tech that we use to improve ad targeting to disease prediction is a no brainer to anyone whose cushy job doesn't depend on the current medieval sta…

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?

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