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%.
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.