Prevention vs Cure

There are people who believe that cancer is largely a preventable disease, and there are people like me.

I think cancer prevention is a worthy cause. In my time as a medical physicist I concluded that we were so good at radiotherapy already it would make more sense to put the money that was being spent on people like me and put it into anti-smoking campaigns. So I went back to pure physics after that, before getting involved in computer assisted surgery.

But smoking is uniquely terrible as a cause of cancer. Tobacco–a naturally occurring leaf, very slightly enhanced by selective breeding–is full of nasty stuff, and burning it to create even nastier combustion products and then sucking the whole lot into your lungs is not the best thing for your health. Among other things, tobacco is rich in potassium, and about 1% of potassium is a long-lived isotope that is left over from the supernova explosion that made the heavy elements that constitute the Earth and all that’s on it. So about 10% of cancers caused by smoking are due to naturally occurring radioactive potassium coming into contact with exquisitely radio-sensitive lung tissue.

Other causes of cancer are not so significant. The article linked above gives some absolute numbers on cancer prevention in the UK, but doesn’t give them as a fraction of all new cancer cases. When you look the numbers up, it turns out that those 57000 preventable cancers add up to about 16% of the 357,000 new cases that occur in the UK annually. Not a bad number, but a long way from a cure, too.

It may not make sense that we focus our resources on cures rather than prevention, but what makes sense has nothing to do with what’s best. There are at least three reasons to focus on cures rather than prevention:

  • A cure would be a cure. It would get rid of the damned disease for good. We are quite close to that, thanks to CRISPR technology and decades of work in fundamental biology.
  • While it is still debated, it appears likely that around half of all cancers are not preventable. That puts a definite floor under the lowest rate we can get from prevention programs.
  • Changing human behaviour is hard. The Soviets killed tens of millions. The Chinese communists tried hard to match that number. Christians and Muslims have been torturing and killing people for centuries without notably diminishing the number of sinners, heretics, and apostates. Governments have been engaged in a “war on drugs” for decades without reducing the rate of use below that seen in Portugal, which effectively decriminalized everything twenty years ago.

It’s easy to criticize research choices, but the arguments for pursuing prevention just aren’t that good compared to the arguments for pursuing a cure. Nor does citing a single case of a person with high radon levels add any credibility to the argument.

Arguments are about facts. Facts are distributions. An anecdote is not a fact, because it is not a distribution.

“This person who had high radon got cancer” tells us nothing about what caused her cancer. It could have been a cosmic ray, or other naturally occurring background radiation. It could have been something she ate. It could have been genes. It could have been bad luck. Singling out one risk factor and saying, “This must have been the cause” serves no good purpose. It does not establish this as a case of preventable cancer, because that can almost never be done. That’s the nature of statistical reasoning.

So while I think we should continue to pursue the major known causes of cancer–smoking and drinking, in particular–we should put the majority of our resources toward finding a cure. We’re very close now, and when the cure is found, it will benefit everyone, not just that half or so of the population whose cancers are preventable.

About TJ

Scientist, engineer, inventor, writer, poet, sailor, hiker, canoeist, father.
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