Cancer survival rates are misleading
56 comments
·October 28, 2025gruez
mr_toad
> notably randomized controlled trials that compare mortality.
Putting people into a control group so you can observe the effects of not treating them might not make it past the ethics committee.
WorkerBee28474
You don't not treat the control group. You give the control group the current standard treatment, and you give the experimental group the new trial treatment.
thayne
In some cases, the "current standard treatment" is no treatment.
gus_massa
Now everyones agree with you and there are no more cases like https://en.wikipedia.org/wiki/Tuskegee_Syphilis_Study (hopefuly).
In the current trials a part of the subjects get the new experimental drug and the control group get the current state of the art treatment.
mr_toad
Yes, but when you compare treatments A vs B for trial 1, and then B vs C for trial 2, and then C, vs D for trail 3, you might not get the same results as comparing A vs D, especially when there may have been other changes in between the three trials (different ages, lifestyles etc).
This is a real problem when the Minister wants to know if it’s worth spending money on treatments, because all you have is a disjointed set of trials, none of which are necessarily representative of the population at large, or the population wide incidence of the disease (assuming there is even data on that (notifiable illnesses are the exception).
standardUser
Randomized controlled trials are a bummer of a 'gold standard'. Extremely expensive, extremely slow and in many cases absolutely impossible. I'm not an AI true believer, but I do hope it offers an alternative or at least enables some desperately needed efficiencies.
duskwuff
"Parachute use to prevent death and major trauma when jumping from aircraft: randomized controlled trial"
https://www.bmj.com/content/363/bmj.k5094
But seriously: this is a recognized problem in medicine and there's already a widely used solution. Whenever you're doing trials of an intervention for a condition which already has an accepted treatment, you run a trial to compare your new intervention to that, and see if your test group has better outcomes. After all, the question shouldn't be whether your treatment is effective; it's whether it's better than existing treatments.
Trials against a placebo have a purpose, but they aren't the only way to run a trial.
saalweachter
It also helps to actually go back and look at in terms of "rejecting the null hypothesis".
If you're talking about a treatment for The Common Cold, the null hypothesis is "the subject got better after awhile because people get better after awhile", and you can't disprove that's what's happening without a very rigorous study with a well designed control.
If you're talking about "here's some robot eyes that cure blindness", you don't really need a control group to test if it works. The null hypothesis is they're blind; you just need to demonstrate they can see to disprove the null hypothesis and prove efficacy.
thayne
Ok, suppose the current standard treatment is A. You have a new treatment B that is 100x cheaper than B, and doesn't trigger allergic reactions that some people have to A. You test against A, and the B group has slightly worse outcomes overall than A. Does that mean that B is useless? What if it is almost as effective, but it's lower cost means more people would be able to use it?
"better" is not a total order, one treatment may be better in some ways and worse in other ways. Especially if you include things like cost and availability.
standardUser
And years later we may have some useful data, if a study can be conducted ethically in the first place. Meanwhile, the environment around us continues to change at a pace the likes of which humans have never experienced. Whatever this era of LLMs does (or does not) do to improve the situation, I am firmly confident that years-to-decades-long human testing is not the endgame of medical science, but rather a long and inconvenient pitstop. There's a lot of those in the history of medicine.
thayne
I'm surprised this doesn't really talk about the thing that was most obvious to me: assuming the 5 year survival rate is five years from diagnosis, that means that if a tumor is diagnosed earlier, even if the cancer kills you, your death is more likely to be outside the five year window.
So for example, if you have (hypothetically) an untreatable cancer that would take six years to kill you, if it is diagnosed right away, you would be counted as a survivor, but if you are diagnosed at year five, you'll only survive a year.
dumb1224
Tumour evolution and progression is complex, being diagnosed early does not guarantee a linear growth. Even when it's biopsied at a timed interval you can't get a full picture of the cancer (invasive pattern etc) evolution trajectory. In some cases low grade tumours will be put on surveilance without radical treatment.
Diagnosis is complex too, you don't want the test to have low specificity. False positive is sometimes tolerated.
nyeah
I think this is a technical article about a narrow aspect of public health policy, not advice to individual patients.
One point in the article is that early detection would give you more years to live even if there were no treatment. Because "early" means "more years". This wasn't obvious to me right away.
But he is not saying don't get screened! He is not saying there are no cancer treatments! He's saying that the 5-year survival rate, considered alone, is a tricky measure that can fool our intuition. In my case he's right.
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Details.
Dumb toy model. Let Tumor X kill you exactly 8 years after it becomes detectable in screening. Assume screening is 100% accurate with no false positives. Assume X cancer kills you exactly 2 years after it causes symptoms. Imagine that there is no treatment for X cancer.
In this dumb model, everybody dies at exactly the same time after the tumor became detectable. The people who caught it in screening had more warning, but otherwise they didn't get a better outcome. Even though screening boosts the 5-year survival rate from 0% to 100%.
Never mind his like 7-state Markov model. OMG. Why.
melagonster
Because for some types of cancer, the stage of cancer is important. A cancer should reach a late stage to kill the patient.
grumpy-de-sre
Colon cancer is an interesting one, Hank Green [1] recently covered a new paper [2] that showed a massive reduction in colon cancer risk for folks that engaged in moderate, regular, exercise. The authors speculated that mechanical stress leading to increased shedding might play an important role.
Weirdly enough that's the same mechanism hypothesized to play a partial role in why breast feeding is also associated with a reduced cancer risk.
Fascinating, weird, stuff.
lm28469
imho if you don't exercise regularly and don't eat clean you're asking for troubles and simply can't complain about your health. The vast majority of people seem not to care until they get a serious diagnostic, by that time you can barely mitigate the issue. It certainly isn't a silver bullet, but at least it stacks the odds in your favor.
Sammi
But that's haaard. Can't I just do the easy solution instead? Don't you have a pill I can take or something?
Aldous Huxley was correct, we truely are amusing ourselves to death. The new meta glasses are really scaring me.
Sorry for the doomerism. There's lots of other stuff to be optimistic about. Maybe this is just an evolutionary filter. Those that fit into these new circumstances will survive.
lm28469
We managed to convince my almost 70 years old father in law, he dropped 30+ kilos in two years. He could barely walk without getting out of breath, now he walks 20-30k steps a day, every day. We got rid of his cardiologist who kept telling him to take pills because his symptoms were just due to old age... Now he needs half the pills, and the ones he still has to take are much lower doses.
No idea if it'll have an impact on his lifespan but it definitely bought him years of health and changed his day to day life
grumpy-de-sre
I mean as long as you don't put systematic barriers in the way of doing the right thing, eg. missing sidewalks and food deserts.
philipallstar
A food desert is defined as food still probably closer to you than a lot of people had in Huxley's day.
uwagar
well india has such low cancers and people there dont exercise much.
ian-g
Of course they're misleading. What did the doctor tell us when my mom was diagnosed? Don't do research, do not trust Dr. Google, Dr. Google lies. At best, Dr. Google is behind the times.
The specifics of your case will strongly affect what happens to you. And even for cancers that are a guaranteed death sentence, survival has increased significantly in recent years.
chrisweekly
Only life itself carries a "guaranteed death sentence".
ian-g
You tell that to everybody with a glioblastoma.
Go ahead, tell them the aggressive mass in their brain, the thing that shortened whatever potential life expectancy they had to, at best, single digit years, isn’t a guaranteed death sentence.
They’ll be so comforted by the idea that maybe their already shortened life expectancy will be further reduced by a car accident or some idiot with a knife.
chrisweekly
Perfect example. I myself survived a grade 4 GBMO. "5-year survival rate: 10%, median life expectancy: 18 months." That was 13 years ago next month.
Your idea that hope is going to lead to a car crash? or murder by knife? is one of the most bizarre and ridiculous things I've ever read.
travisjungroth
This article is a criticism of reasoning, not health advice or suggestions for cancer screening. Maybe he should put a big warning at the top, rather than explain it throughout. A lot of people seem to be missing it.
We're so used to argument that criticizing logic is taken as criticizing the conclusion.
tptacek
The only thing the author seems to be directly arguing against is speculative full-body MRI scanning, which is already mainstream medical advice, for many of the reasons he offers.
bonsai_spool
> We're so used to argument that criticizing logic is taken as criticizing the conclusion.
This may be so, but his examples are so poor that one is distracted from any type of subtle claim he would make. They are bad in obvious ways (every cancer patient is staged, but we pretend in the article like staging is ancillary to researching survival rates).
dkural
This article, in the world as it exists right now, is wrong about colon cancer. Anyone reading this of a certain age: get that colonoscopy, and those polyps removed. Snip it in the bud. That's the great thing about a colonoscopies - all-in-one screening + treatment.
Evidence: https://www.nejm.org/doi/full/10.1056/NEJMoa1301969
Large prospective cohorts (Nurses’ Health Study + Health Professionals Follow-Up Study) with long follow-up - screening colonoscopy was associated with a 68% lower risk of death from colorectal cancer overall (multivariable HR ≈ 0.32, 95% CI 0.24–0.45) and showed significant reduction for proximal colon mortality as well (HR ≈ 0.47, 95% CI 0.29–0.76).
travisjungroth
> For colon cancer, the rates from the SEER data are are 91%, 74%, and 16%.
This is the only claim the article makes directly about colon cancer. Otherwise, it's saying that early detection being beneficial isn't supported by survival rates alone.
nyeah
"Otherwise, it's saying that early detection being beneficial isn't supported by survival rates alone."
That claim may be obvious to everybody except me. Anyway it turns out to be true.
tptacek
Weirder still that Taleb misses the base rate flaw in the logic of full-body MRI screening and cancer screening, an observation that is pretty up his alley and is kind of a well-known thing in this domain.
DebtDeflation
Near as I can tell, the only valid point the author makes is that since mortality rates increase as cancer progresses stages and since progression through stages takes time, a 5 year mortality rate is not a great metric and it would be better to also have 10 and 15 year mortality rates to determine the degree to which early detection + treatment actually increases life expectancy.
1970-01-01
So their entire argument is statistics does not tell the entire story. Didn't we all learn this truth when we learned statistics?
tptacek
I don't think it's nearly as obvious as that; the same misunderstanding of 5-year survival statistics also biases international health system comparisons --- countries can look like they're really good at treating XYZ cancer, but in fact only be better at detecting it at an earlier stage.
scythe
>The purpose of the model is to show that we can reproduce the survival rates we see in reality, even if there are no effective treatments.
That's a great argument in the abstract, but it ignores the fact that there are effective treatments for colon cancer. The fact that we can reproduce real survival rates in a counterfactual world where there are no effective treatments for colon cancer does not actually give us a model of the real world because the counterfactual explicitly contradicts known scientific facts.
What you have to do in order to make this argument is to show that there are Markov models where early detection does not work despite the fact that some cancers will cause death if untreated and not if treated. You cannot simply rely on models that have clearly impossible transition probabilities. You need possible models. Or you have to show that the absolutely massive amount of scientific literature and clinical experience about how to treat colon cancer is somehow flawed.
Some people are defending this because the blog post is attacking a specific argument, but I don't see how that can work. I am pretty sure that Nassim Taleb and most other people who are capable of putting together a coherent statistical argument (even a flawed one) understand that colon cancer can be treated sometimes.
standardUser
> Because it is based on past cases, it doesn’t apply to present cases if (1) the effectiveness of treatment has changed or – often more importantly – (2) diagnostic practices have changed.
This was my key takeaway. In a society organized around statistics, we're struggling through an era where those statistics expire faster everyday, and faster than new data can be generated. I can almost relate to the mindset that devalues "facts" because they're increasingly complicated, rapidly changing and come with too many caveats.
>To be clear, all of these conclusions can be true, and in some cases we know they are true, at least in part. For some cancers, treatments have improved, and for some, additional screening would save lives. But to support these conclusions, we need other methods and metrics – notably randomized controlled trials that compare mortality.
the economist put out a piece a few months ago providing just that. Specifically it compares overall cancer mortality rates (and more interestingly, mortality rates adjusted for age) and shows that cancer deaths have been dropping.
https://www.economist.com/briefing/2025/07/17/the-world-is-m...
https://archive.is/TNjoi