Friday, January 23, 2015

About half of all cancers are just bad luck. It's not your fault.

There's been a lot of talk recently about a paper claiming that two thirds of all cancers are due to bad luck [Bad Luck of Random Mutations Plays Predominant Role in Cancer, Study Shows]. The take-home message was that you could get cancer even if you ate "healthy," took lots of vitamins, didn't smoke, and went to the gym every day. That's not what people wanted to hear.

But scientists have known for decades that many cancers are due to random mutations that just happen. These cancers are not hereditary and are not caused by the environment. There's nothing new here.

That didn't stop a number of people from criticizing the article and some of the criticisms were justified. Nevertheless, what the article showed was that cancers tended to occur more often in tissues with lots of cell divisions (and DNA replications). That's exactly what you expect if random mutations due to replication errors are the cause of the cancer mutations.

David Gorski of Science-Based Medicine sorts it all out for us [Is cancer due mostly to “bad luck”?]. Please read his lengthy article if you want to understand the issues. David Gorski concludes ...
It’s understandable that humans crave explanation, particularly when it comes to causes of a group of diseases as frightening, deadly, and devastating as cancer. In fact, both PZ Myers and David Colquhoun have expressed puzzlement over why there is so much resistance is to the concept that random chance plays a major role in cancer development, with Colquhoun going so far as to liken it to ” the attitude of creationists to evolution.” Their puzzlement most likely derives from the fact that they are not clinicians and don’t have to deal with patients, particularly given that, presumably, they do have a pretty good idea why creationists object to attributing evolution to random chance acted on by natural selection and other forces.

Clinicians could easily have predicted that a finding consistent with the conclusion that, as a whole, probably significantly less than half of human cancers are due to environmental causes that can be altered in order to prevent them would not be a popular message. Human beings don’t want to hear that cancer is an unfortunately unavoidable consequence of being made of cells that replicate their DNA imperfectly over the course of our entire lives. There’s an inherent hostility to any results that conclude anything other than that we can prevent most, if not all, cancers if only we understood enough about cancer and tried hard enough. Worse, in the alternative medicine world there’s a concept that we can basically prevent or cure anything through various means (particularly cancer), most recently through the manipulation of epigenetics. Unfortunately, although risk can be reduced for many cancers in which environmental influences can increase the error rate in DNA replication significantly, the risk of cancer can never be completely eliminated. Fortunately, we have actually been making progress against cancer, with cancer death rates having fallen 22% since 1991, due to combined efforts involving smoking cessation (prevention), better detection, and better treatment. Better understanding the contribution of stochastic processes and stem cell biology to carcinogenesis could potentially help us do even better.


17 comments :

  1. Hi Larry. Thanks for the link to another interesting discussion of this paper. Personally, I wasn't surprised by the overall finding and I hope it might help balance out the public perception that their cancer must be due to a "faulty" gene or environmental factor. Bad luck must be an accurate description for a great many cancers.

    All that said though, their methods are a little odd, especially when they try and split cancers into two groups. This leads them to state that the incidence of some cancers are poorly explained by the number of cell divisions when figure 1 shows that's clearly not the case. I've blogged about it at the address below if you or ypur readers are interested.

    https://cgatoxford.wordpress.com/2015/01/09/cancer-correlations-and-clustering/

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  2. There's one thing that may change he result a little. Behavior can have an effect on the rate of cell proliferation in some tissues and so influence cancer frequency without resort to mutagens.

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  3. So you cannot eliminate the probability of getting cancer, but you can definitely increase the probability.

    Or put in a more positive light, you can eliminate things that could double your risk.

    My math illiteracy may be showing, but that's how I read it. Corrections welcomed.

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    1. If you don't smoke, don't work in a coal mine, and have parents with good genes, there's not much else you can do.

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    2. Also, use sunscreen and get any radon gas out of your home.

      I've been teaching for years that most cancers are caused by bad luck (unpredictable and unavoidable mutations that happen to occur in genes that affect cell behaviour), so I too was really surprised by the resistance to this paper's conclusions.

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    3. Well smoking used to be a majority activity. I smoked for eight years. Just passed the 40th anniversary of quitting. My mother-in-law smoked and died of lung cancer.

      So there's not much and individual can do, but there are lots of things regulated or forbidden due to cancer risk. I'd like to see a scientific assessment of these regulations. I suspect that most are bogus. The added risk just doesn't justify being banned.

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    4. There's a lot more to prevent cancer that you can do other than "don't smoke, don't work in a coal mine". Even assuming that the results from the study are correct and 50% of cancers are not linked to behavior, this implies that 50% are. Diet and exercise aren't panaceas, but there's pretty solid data showing both diet and obesity are linked to cancers (not to mention heart disease, the other major cause of death in the developed world).

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  4. This claim may very well be true but I have my doubt as to the degree of the influence of environmental factors in relation to cancer. This is totally not my area of expertise, so I'm going to relay on others, but I remember once going over some statistics related to prostate cancer rates in Asia and US. I don't remember the exact details but it must have been overwhelming since I remember some. Up until 1958 or so there were 18 cases of confirmed prostate cancer deaths in Japan in comparison to US of 14000 or 140.000. I'm sorry but all my notes are at the office and I'm at home now. My point is, how does this statistic fits into the picture of random mutations if by 1990 Japan almost reached the same level of prostate cancer deaths with US? I'm puzzled but many studies "suggest" that dietary changes influenced by the American life style and eating habits are the only reasonable answer to this dilemma.

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  5. I only know about this from common observation.
    Yet the point in all these things to me is how they imply cancer is a chance thing. When clearly it comes from old age or rather the decay of the body.
    Our immune system etc simply gets worse and cancer breaks in.
    Not a strange mutation out of thje blue but a predictable thing.
    I see this weakness as the big point.
    Then radiation, smoking, other things, can affect/create cancer because they weaken the defense.
    I think cigarettes are as harmless as chocolate chip cookies.
    Its more likely the minor irritation of tobacco , in old age and after long time impact, has beat down the resistance and so cancer comes. Yet smoking is actually harmless if one did it moderate and stopped at say 55 or something.

    anyways it seems they see cancer as like a germ in how they say it affects people
    It seems clear its all about our resistance to it. Age and some heritability.
    very little environmental origins at least before old age.
    Unfortuately everone would get deadly cancer if we lived long enough. Say up to 150. .

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    1. Byers says: "I think cigarettes are as harmless as chocolate chip cookies."

      Yeah, but do the progressive radicals who run the guvmint make the Keebler elves put warning labels on their cookies? Oh nooo. The liberals rail against discrimination, meanwhile they discriminate themselves against human-Americans in favor of elves. Why? Just because they live in a tree like a bunch of damn Injuns! Or communists!

      Our immune system etc simply gets worse and cancer breaks in.

      Yup. There you go. Our immune system normally would protect us against tumors, that's totally how it works. The immune system normally identifies neoplastic tissue and destroys it with white blood cells. But eat too many cookies and they destroy your immune system like that AIDS that God gave to the sodomites. Eat too many cookies and bang, you've got a prostate the size of a supermarket pomelo.

      That's totally scientific. It's so scientific I could die from an overdose of all the totally real science. I could have a heart attack from all that science. I could get a tumor from consuming too much of Byers' science.

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    2. P.S. Next time a girl scout rings my doorbell, I'm getting out the baseball bat!

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  6. Up until now I was giving you the benefit of the doubt but now I realize that you are a kook. You don't have anything to contribute to these discussions.

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  7. @Diogenes I know you meant well with your sarcastic comment "Our immune system normally would protect us against tumors, that's totally how it works. The immune system normally identifies neoplastic tissue and destroys it with white blood cells." but this turns out to be pretty close to the mark. Do a quick search on "immunoediting" and also look at drugs targeting the PD1/PDL1 axis.

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    1. Wow! This is interesting

      How come the immune system fails then? I recall reading that there are "10 layers of protection" that cells have to overcome before becoming cancerous. Is that true?

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  8. In any case, there seems to be a tendency to say that people who get cancer because they had an unhealthy addiction such as smoking "deserve" to have cancer. I've always found this to be an ugly way of thinking. Nicotine is extremely addictive. Some people are able to kick it, some aren't. People who have managed to kick heroin have said that nicotine is harder to quit. Nobody deserves to suffer and die from cancer.

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    1. I was a light smoker for a mere 8 years. Quitting was by far the hardest thing I ever did. I craved a cigarette every waking minute of every day for a year and a half.

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  9. Where do I find the actual course? All I can get is this silly video.

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