Prolonging the expected lifetime by several years nontrivially improves chances of surviving until better drugs are found, and ultimately long term survival. Our ability to cure cancers is not constant, we're getting better at it every day.
Even so. Current first-line treatment for pancreatic cancer is surgery, because chemo doesn't really help a lot. Chemo alone is useless in this case. So any kind of treatment that does have a hope of treating anything involves removing the pancreas.
Take those 99% false positives. If you just remove the pancreas from everyone, you remove 20 years of lifetime through severe diabetes. In terms of lost life expectancy, you killed up to 25 people. Surgery complications might kill one more. In all, totally not worth it, because even if you manage to save everyone of those 1% true positives, you still killed more than 20 (statistical) people.
And the detection rate might be increased by more testing. But it needs to be a whole lot more, and it won't help. Usually pancreatic cancer is detected in stage 3 or 4, when it becomes symptomatic, 5 year survival rate below 10% (let's make it 5% for easier maths). The progression from stage 1 to stage 3 takes less than a year if untreated. So you would need to test everyone every 6 months to get detections into the stage 1 and stage 2 cases, that are more treatable. Let's assume you get everyone down to stage 1, with a survival rate of roughly 50% at 5 years, 15% at 10 years. We get a miracle cure developed after 10 years where everyone who is treated survives. So basically we get those 15% 10-year-survivors all to survive to their normal life expectancy (minus 20 because no more pancreas). Averaging they get an extra 10 years each.
Pancreatic cancer is diagnosed in 0.025% of the population each year. In the US at 300Mio., thats 750k in 10 years. With our theoretical miracle cure after 10 years for 15%, that is a gain of 1.125Mio years lifetime. A 1 hour time needed for testing per each of 300Mio people twice a year for 10 years already wastes 685k years of lifetime, so half the gain already. That calculation is already in "not worth it" territory if the waiting time for the blood-draw appointment is increased. That calculation is already off if you calculate the additional strain on the healthcare system, and the additional deaths that will cause.
