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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

#261

Post by TaupeRanger »

AlexCoventry wrote: post #259
TaupeRanger wrote: post #96

Earlier quoted context omitted.

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:…

Good question. The proof is in the pudding. Run a well powered RCT and if the intervention helps patients live longer and/or better, then we should consider using it! It will be hard to design a study that includes all possible detected cancers, but there are ways around this - perhaps we begin by studying those cancers that are most common and lethal, and go from there.

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

#262

Post by nybble41 »

jacquesm wrote: post #59
ggrrhh_ta wrote: post #55

Earlier quoted context omitted.

BTW... years ago I was rather supportive (albeit not having voiced it) of the argument that false positives lead to unnecessary interventions and thus screening should be itself gated.

Your understanding as evinced by the comment above leaves me to wonder if you actually get that this is not about individual outcomes but about the overall statistics. Even if more accurate tests would turn up more true positives that still would not necessarily result in increased patient outcomes. That is why absent symptoms testing makes sense for only a very low number of cancers where early detection does improv…

> absent symptoms

A positive blood test is a symptom. One which you'll miss if you don't do the blood test regularly.

And looking for symptoms (other than a blood test) is a form of testing... one with much worse accuracy (both positive and negative) than the blood test, especially in the early stages.

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

#263

Post by randcraw »

nevinera wrote: post #159

0.5% false positive rate is actually quite high. I don't have the numbers, but I'd be surprised if more than 1% of the people that would receive such a screening actually already have cancer , which would mean that it produces about as many false positives as false negatives. Picture a population of a million people, all receiving the test. 1% of them have cancer (unknown to them) - half of those people get a negativ…

I would very much like to know the confusion matrix for all these component tests: the false positive rate, false negative rate, i.e., the sensitivity and specificity of each.

For example, the Prostate Specific Antigen (PSA) test is famous for a high false positive rate, inviting many men to worry needlessly or get unwarranted biopsies. The current state of any test and its history are important to know for both patient and doctor, so both can have an informed dialog about the options after a positive result.

Also, each of these 50 tests are going to evolve over time, as will the accuracy of error rates for patient subpopulations. Race, age, ethnicity, co-morbidities and co-maladies will each shift the accuracy and precision of each test in ways that will make them much more useful if everyone stays well informed about all their merits and demerits.

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

#264

Post by bluGill »

rwmj wrote: post #178
bluGill wrote: post #164

Earlier quoted context omitted.

That this test is approved implies that it to some extent at least makes people live longer. There are a number of cancers that are easily treatable in stage one - but they have no symptoms then, and so often kill people because by the time it is discovered it is too late. False positives are a concern, but one that is manageable. People should get regular checkups, if something comes up we just do more testing as ne…

It's approved to be rolled out to a medical trial. You can read what the journal says here: https://www.annalsofoncology.org/article/S0923-7534(21)02046...

I'll stand corrected.

Though that makes this discussion completely worthless - without trial results we have no idea if it is a useful test. Once we have those results we will know something about how useful/useless might be.

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

#265

Post by handmodel »

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'm not sure.

I weight myself everyday. Some people tell me not to do that but its honestly pretty good at keeping me in check and because I weigh myself everyday I know that sometimes I just get super bloated and put on four pounds of water and it will be gone in a couple days. When you get more data you learn to adjust how you interpret it and make better decisions.

Likewise, if getting a false result 50% of the time becomes common (this assumes we never improve the tests) then people will know to adjust their priors. After all - I've had to go to specialists a few times for extra tests. I wouldn't say we ban those.

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

#266

Post by iNane9000 »

TaupeRanger wrote: post #218
fallingknife wrote: post #186

Earlier quoted context omitted.

> 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…

You are assigning beliefs to me that I do not hold. As I said, we would need a solid randomized controlled clinical trial to determine whether any particular intervention actually helps patients live longer and/or better. That's the only way we know. So go ahead and collect data, do an RCT, and let us know how it goes.

The problem with this and the nnt gatekeeping is that personalized medicine will always require stepping away from massive double blind randomized placebo controlled multiple meta study levels of evidence. From a patient perspective it feels a lot like economics largely determine medical outcomes.

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

#267

Post by TaupeRanger »

throwawaynotmd wrote: post #258
bryan0 wrote: post #245

Earlier quoted context omitted.

> 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.

That is not how medicine works, especially with cancer. Very often we simply don't know whether or not to "ignore" something. But the harms of knowing are not zero, and therefore screening can itself be a net negative. That's why a well powered RCT is required to say whether it benefits patients or not.

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

#268

Post by jacquesm »

nybble41 wrote: post #262
jacquesm wrote: post #59

Earlier quoted context omitted.

Your understanding as evinced by the comment above leaves me to wonder if you actually get that this is not about individual outcomes but about the overall statistics. Even if more accurate tests would turn up more true positives that still would not necessarily result in increased patient outcomes. That is why absent symptoms testing makes sense for only a very low number of cancers where early detection does improv…

> absent symptoms A positive blood test is a symptom. One which you'll miss if you don't do the blood test regularly. And looking for symptoms (other than a blood test) is a form of testing... one with much worse accuracy (both positive and negative) than the blood test, especially in the early stages.

Just so we are using the same definitions for the words we write, here is the definition of 'symptom' in a medical context:

https://www.cancer.gov/publications/dictionaries/cancer-term...

"A physical or mental problem that a person experiences that may indicate a disease or condition. Symptoms cannot be seen and do not show up on medical tests. Some examples of symptoms are headache, fatigue, nausea, and pain."

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

#269

Post by TaupeRanger »

tnel77 wrote: post #241
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…

For every genuinely smart person on HN, there’s a handful of Google warriors who hardly know what they are talking about. I guess that’s not unique to HN, but it can be aggravating just how many commenters can be so “know-it-all” with their comments.

Try making an actual argument rather than simply attacking the attitude or character of the person you're responding to.

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

#270

Post by jacquesm »

msrenee wrote: post #228
Clampower wrote: post #10

Earlier quoted context omitted.

This is not true in the Netherlands. You don’t get any tests if there is nothing wrong. Healthcare in this country scares me.

No mammograms? No pap smears? No prostrate screening? That's shocking.

We do all of those, but they're all voluntary (as they should be), there are regular drives for all of these.
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