For instance, prostate cancer blood screening often led to radical treatments that are no longer thought to be worth it for most people.
> most prostate cancer grows so slowly, if it grows at all, that other illnesses are likely to prove lethal first
https://www.nytimes.com/2023/05/08/health/prostate-cancer-sc...
In the case of pancreatic cancer, it is much more aggressive and you need to catch it early.
It's not clear that the cancers that you would find early with a more sensitive test are those more aggressive cancers.
The pancreatic cancers we find with our current detection (generally after becoming symptomatic) are typically quite aggressive. But are they all the cancers? Likewise, if the cancer is aggressive, it can grow quite a bit between screening intervals and not be found all that early.
(Part of why we think that "finding cancer early" is such a benefit is that because the smaller/earlier cancers we find are less aggressive than the cancers that we first find when they're huge and spread. There is definitely an effect from earlier detection but our estimate of it has been confused by this effect.)
As we've increased cancer screening, we've found that survival rates have gone up, as have survival times after detection... but unfortunately we've often also found that the screening doesn't always reduce the number of people dying of that cancer at a certain age. Instead, you find more cancers, and you find them earlier so more people live to 5 years, even if you've changed nothing. Cancer treatment has gotten better, but most of the benefits we have expected from better cancer screening have not materialized.
Finding pancreatic cancer early sounds good. And it may be able to reduce mortality from pancreatic cancer, but it's not a sure thing.
So his advice was, don’t look, don’t treat. Either you have the slow one and treatment is harmful, or you have the fast one and you’re going to die soon anyway.
As you mentioned, the outcomes aren't significantly different, regardless of how you treat it.
From the article linked above:
> Researchers followed more than 1,600 men with localized prostate cancer who, from 1999 to 2009, received what they called active monitoring, a prostatectomy or radiation with hormone therapy.
Over an exceptionally long follow-up averaging 15 years, fewer than 3 percent of the men, whose average age at diagnosis was 62, had died of prostate cancer. The differences between the three treatment groups were not statistically significant.
The measurements are not independent and the quality of the measurement is not improved by this.
> you can confirm it with another method.
Yes. And usually the other method is invasive and expensive and bears some risk.
And then you get results like the blood test saying "very likely cancer" and the biopsy saying "uh, probably not?" that you need to decide what to do with.
That's the errant part. A small amount of the false positives will be because of lab issues. The rest will be because this patient is different in some way, but not all of them are cancer. Medicine doesn't have very many perfectly specific tests.
So you have a patient who has some weird enzymes around because they're genetically different, for example, and they always pop positive on this particular test. Or has an unusual diet that causes some other non-tested-for-enzyme level to be high enough to set off this sensor. Or whatever.
In this case, the specificity is 98%, so this false positive rate is about 2%.
https://www.uspreventiveservicestaskforce.org/uspstf/recomme...
We haven't even solved the most basic shit like shelter, food, education, &c for millions of people in the west, as a society we're faaaaaaaaar from universal yearly full health checkups. As an individual feel free to get private checks, they'll gladly take your money
This has a huge GDP cost in the USA, that needs to be addressed. The causes are big pharma/hospo/AMA/insuro/lobbyo.... One wonders why the AMA is there? - they limit the numbers of doctors trained in Universities/training hospitals to forestall price competition among doctors by various means. Dentists do the same.
https://www.healthcare.gov/coverage/preventive-care-benefits...
The recommendations tend to take these into account, and then you and your doctor adjust.
Sometimes politics gets into it, like with the recent changes to breast cancer recommendations, but, overall, it works well for many people.
Could you elaborate on this?
The earlier you screen, the worse this is, since the ratio of false positives vs true positives gets higher and higher, for example 1000 vs 5 or 10000 vs 5.
I'd assume the chances of getting a second false positive if you already got one are much higher.
For better or worse, under the American healthcare system, the patient pays for those tests, sometimes covered by insurance. If the tests are paid for out of pocket by the patient, is there still such issue?
To reframe it from the individual patient's perspective, when you take a test simply for the sake of screening, there is the chance you'll learn something true that helps you, and the chance you will learn something false that hurts you
ANOVA to pick variables and then reasonably selecting thresholds is a fine process that avoids overfit.
The big problem is, biology is messy and measuring lots of people to find correct thresholds is really expensive and time consuming. It's not really a technological problem, though technology has helped a little.
Prevalence of breast cancer: 1%
Sensitivity (percent of people who have the disease test positive): 90%
Specificity (percent of people without the disease test negative): 91%
And asked, "How many people who test positive have the disease?" (i.e., positive predictive value)
It's only 1/11. I think only 20% got it right (in a 4 answer multiple choice question)
If sensitivity is high and the base rate is low, you can approximate it with .01 / (1-.91).
Or, mental math assuming 10,000 people is not unreasonable for your case (100 with disease, 90 true positives; 9900 * 9/100 false positives.. divide everything by 9 to make it easier, 10 true positives and 99 false positives, or 10/109 or say "9%".
Say that this test has a false positive 1 in 1000 times. If you test 100,000 people, you'll get 100 positives that need invasive further testing and followup, and 5 real pancreatic cancer cases.
Society will pay for 100,000 tests, and 105 cases of followup. You may cause lasting harm to some of those 105 people. And then it's not clear if you can improve the survival of the 5 pancreatic cancer cases much. They'll live longer after diagnosis (because you diagnosed earlier) but not necessarily longer overall.
(One other screening effect: You'll find more "real cancer" that is so slow growing that it may have always remained subclinical before the more sensitive testing; And the most serious cancers, you won't find so much sooner, because they grow so much in the interval between tests.)