3 ms·
Maybe. Let's do a thought experiment. Let's say you do have a positive test for pancreatic cancer. Overall 5 year survival rate 12%, but other than with other
by holowoodman 1y ago
Maybe. Let's do a thought experiment.
Let's say you do have a positive test for pancreatic cancer. Overall 5 year survival rate 12%, but other than with other cancers, people continue to die after that. Basically, it is almost a death sentence if it is a true positive. Early detection will increase your odds a bit, and prolong your remaining expected lifetime, but even stage 1 pancreatic cancer, only 17% survive to 10 years. Let's say you are one of the 99% of false positives, because everyone gets tested in this hypothetical scenario. Let's say imaging and biopsy looks clean. No symptoms (which you typically don't have until stage 3 with pancreatic cancer, where it is far too late anyways). With the aforementioned odds, what would you do?
Panic? Certainly, given that if it is a real positive, you might as well order your headstone.
Panic more? Maybe people with those news will change their behaviour and engage in risky activities, get depressed, or attempt suicide (https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2800688 https://jamanetwork.com/journals/jamanetworkopen/fullarticle... ). All of which will kill some of those people.
Get surgery to remove your pancreas? Well, just the anesthesia as a 0.1% chance of killing you, the surgery might kill 0.3% in total. No pancreas means you will instantly have diabetes, which cuts your life expectancy by 20 years.
Start chemotherapy? Chemo is very dangerous, and there is no chemo mixture known to be effective against pancreatic cancer, usually you just go with the aggressive stuff. It is hard to come by numbers as to how many healthy people a round of chemo would kill, but in cancer patients, it seems that at least 2% and up to a quarter die in the 4 weeks following chemotherapy (https://www.nature.com/articles/s41408-023-00956-x https://www.nature.com/articles/s41408-023-00956-x ). And chemotherapy itself has a risk of causing cancers later on.
Start radiation therapy? Well, you don't have a solid tumor to irradiate, so that is not an option anyways. But if done, it would increase your cancer risk as well as damage the irradiated organ (in that case probably your pancreas).
So in all, from 100 positive tests you have 99 false positives in this scenario. If just one of those 99 false positives dies of any of the aforementioned causes, the test has already killed more people than the cancer ever would have. Even if no doctor would do surgery, chemotherapy or radiation treatment on those hypothetical false positives, the psychological effects are still there and maybe already too deadly.
So it is a very complex calculation to decide whether a test is harmful or good. Especially in extreme types of cancer.
- dgroshev 1y agoProlonging 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.
- holowoodman 1y agoEven 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.
- inglor_cz 1y ago"Let's say you are one of the 99% of false positives, because everyone gets tested in this hypothetical scenario." This alone is a disqualifier for your scenario. A test with 99 per cent of false positives will not be widely used, if at all. (And the original Galleri test that the article was about is nowhere near to that value, and it is not intended to be used in low-risk populations anyway.) I am all for wargaming situations, but come up with some realistic parameters, not "Luxembourg decided to invade and conquer the USA" scenarios.