Blood test that finds 50 types of cancer is accurate enough to be rolled out • Hacker News Board

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

#321

Post by colinmhayes » Fri, Jun 25, 2021, 7:37 PM UTC

moralestapia wrote: post #293

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 feel it's a net win anyway, if the procedure is not invasive and cheap, you could take one every so often (yearly?) and if something shows up you just double check with a better method or w/e. Better than nothing, which is the current alternative.

The problem is people are idiots. They get a false positive and their doctors tells them "well there are a lot of false positives with this test" but all people hear is "you have cancer." Then they get an invasive biopsy because the healthcare system is glad to take your money.

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

#322

Post by matheusmoreira » Fri, Jun 25, 2021, 7:39 PM UTC

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…

> Why can’t we observe ourselves medically and analyze that record for early signs of trouble before it becomes serious?!

Maybe one day we'll have cybernetic implants that can constantly monitor our health. Hopefully it won't turn into a privacy nightmare.

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

#323

Post by vharuck » Fri, Jun 25, 2021, 7:40 PM UTC

lhorie wrote: post #305

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…

I think you're casting too wide of a net there. Just because you've detected something early doesn't mean you automatically need aggressive interventions like chemotherapy. The impact might just end up being a line in your medical record for the family physician to keep an eye on during yearly routine exams. Breast cancer awareness programs are a good example of early screening programs not being an exercise in mass…

>Breast cancer awareness programs are a good example of early screening programs not being an exercise in mass hysteria.

This example also shows how screening can be recommended against because that's better for public health. The US Preventive Services Task Force (indirectly decides what Medicaid/Medicare covers) has different recommendations than the American Cancer Society for how often women of certain ages should have mammograms. USPSTF recommends against routine mammograms for women aged 40 to 49 if they don't have other risk factors. ACS recommends biannual mammograms start at age 45.

The reason they differ is because of how they weigh the reduction in deaths against the harm of false positives. Routine mammograms will prevent breast cancer death, no doubt about it. But notice neither recommends routine mammograms for all women below 45, even though they accounted for over 10% of breast cancer diagnoses in 2014-2018[0].

The math is tricky when comparing a risk of death against quality of life and economic costs. Public health is a matter of public policy as much as health.

[0] https://seer.cancer.gov/statfacts/html/breast.html

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

#324

Post by Fomite » Fri, Jun 25, 2021, 7:42 PM UTC

throwawaynotmd wrote: post #315

Fomite wrote: post #304

Earlier quoted context omitted.

"More information can never be harmful." In my particular field of biomedical research, there has recently been a push for "Diagnostic Stewardship" because more information has demonstrably been harmful to patient well-being.

It’s not enough to say it’s harmful. How is it harmful? A blood test, for example, cannot be inherently harmful. (Okay, no more harmful than drawing blood). So it must be about what people then decide to do based on that test. That’s what my post is about.

But vanishingly rarely are diagnostic tests given and then the results ignored. That's not how consumers of healthcare nor clinicians work.

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

#325

Post by tyrex2017 » Fri, Jun 25, 2021, 7:52 PM UTC

konschubert wrote: post #22

konschubert wrote: post #17

If you’re tested positive, what’s the probably that you actually have cancer? (The article states 0.5% false positive rate and about 50% true positive rate, but I would need to know the the prevalence of cancer in the population to compute what I am asking for).

Let’s say 1% of ppl have cancer at any given moment - So if we test a random person, there is a 1% * 50% = 0.5% chance that person is tested positive for cancer because they have cancer. And a 0.99% * 0.5% = 0.5% chance that a person is tested false positive. This means if the test shows positive for somebody, it’s about 50-50 that they actually have cancer - correct?

Correct.

Thats why it may be a good idea to test higher risk populations or people with health issues.

It could make the ratio of absolute true positives to false positives 10x better

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

#326

Post by vidarh » Fri, Jun 25, 2021, 7:58 PM UTC

radu_floricica wrote: post #243

vidarh wrote: post #41

Earlier quoted context omitted.

How many people are you willing to kill with too excessive testing programs? Because that is part of the equation too. It's easy to ignore because chances of harm from non-invasive-ish testing like a blood test is low. The problem is that it compounds quickly. Consider: * For a rare condition you need a lot of tests to find them. Let's say you look for something that 1 in a million can be expected to have. * When you…

You're missing a step. There are several responses saying basically the same thing (testing kills), and more or less randomly I'm going to answer yours. All have the same step missing. Testing doesn't kills by itself, not in numbers worth mentioning. Treatments - sure, a whole different ball game, they're positively dangerous. But between testing and treatments there should be a specialist that crunches the numbers a…

> Testing doesn't kills by itself, not in numbers worth mentioning.

Mammography involves radiation and pressure. The radiation alone is a significant risk [1], and kills by causing cancer. It can also cause tumors to rupture and spread malignant cells. It's significant enough to significantly increase the hurdle where mammography is justified. It does not mean it never is - absolutely not. But it means screening programs need to be targeted.

> What I don't get however is how it can get even close to conventional wisdom that you want to avoid testing, as a rule.

It's not conventional wisdom that you want to avoid testing. That is for example what led to a lot of really aggressive campaigns for extensive breast cancer screening.

What we saw was a small improvement in outcomes on a small number of positive test results, for a level of testing that suggested it was necessary to take into account other factors.

Breast cancer screening was rolled back many places, or widening of the age bracket was halted as a result of looking at outcomes and realising that "conventional wisdom", which used to be that more testing was inherently good was flawed.

There are clear, quantifiable harms from it, ranging from actual risks of causing cancer or causing spread of cancer with mammography. These risks are low enough to be worth it for certain patient groups, but high enough to add up to problems if screening is too widespread.

People didn't start worrying about this because it was "conventional wisdom", but because the data shows people actually dying.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4878445/

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

#327

Post by vidarh » Fri, Jun 25, 2021, 7:59 PM UTC

JumpCrisscross wrote: post #221

dabbledash wrote: post #29

Earlier quoted context omitted.

The idea is that treatment also has risks and false positives are an issue. If you gave a mammogram to every 20 year old woman, you would end up doing a large number of unnecessary biopsies and you’d find almost no real cancer. In the end, you’d lose more people than you would save. Or that’s the idea. I’m no expert in this but it makes sense to me conceptually.

> If you gave a mammogram to every 20 year old woman, you would end up doing a large number of unnecessary biopsies and you’d find almost no real cancer If you gave a mammogram to every 20-year old, you wouldn't do a biopsy when you got a positive. You'd increase monitoring and maybe suggest lifestyle changes. The same way we don't immediately catherize everyone who comes back with high cholesterol.

If you gave a mammogram to every 20-year old, you'd cause a significant increase in cancers:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4878445/

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

#328

Post by throwawayboise » Fri, Jun 25, 2021, 8:05 PM UTC

lhorie wrote: post #305

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…

I think you're casting too wide of a net there. Just because you've detected something early doesn't mean you automatically need aggressive interventions like chemotherapy. The impact might just end up being a line in your medical record for the family physician to keep an eye on during yearly routine exams. Breast cancer awareness programs are a good example of early screening programs not being an exercise in mass…

"The impact might just end up being a line in your medical record for the family physician to keep an eye on during yearly routine exams."

And something to be on the back of your mind as a worry forever. I'd rather not know.

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

#329

Post by vmception » Fri, Jun 25, 2021, 8:05 PM UTC

dryrun wrote: post #36

vmception wrote: post #8

Earlier quoted context omitted.

That’s not good enough for cancer because we dont even know how fast or slow it grows. Even if it cancer cells multiplied at the rate of a fetus that would be too fast for an annual physical. Congratulations, death. Ideally something like a wearable computer or nanomachines in your blood stream automatically report anomalies for individualized treatment.

Given the amount of "I don't want bill gates injecting me a tracker!", I have some idea of how a conversation with the same people about nano machines in their body would go. I would also bet on the time-frame between this and the availability of your data on the servers of your health insurance.

Not my problem, human cancers stay in there own bodies and are not communicable

To our knowledge

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

#330

Post by vidarh » Fri, Jun 25, 2021, 8:07 PM UTC

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…

We have done this for e.g. breast cancer, and that is exactly why people are cautious now, because we have real data on the harm overtesting can cause. That doesn't mean it should never be done, but that it needs to be approached with care.