About the ‘Discovery’ that Chance is the Most Important Cause of Cancers

I like my use of the word ‘Chance’ and ‘Cause’ as related.

But before I go further, I must indicate where my attention was first drawn to the study in question. I think that it was Frank Davis, but I’m not sure. That connection led me to Chris Snowden, and, eventually, to Simon Cooke. (The links are in the sidebar).

It is true that I have little to add to the comments elsewhere, but, I must admit that I find it impossible to resist.

So let us get at the fundamental idea. In some parts of the human body, cells die and are replaced far more often than in other parts. In the colon, cells die and are replaced lots of times, whereas in the intestines the cells last a lot longer before dying and being replaced. The research showed that cancer occurs most often in those parts of the body where there is rapid death of and replacement of cells. Cells which die are replaced by stem cells, which have the ability to change into whatever type of cell is required in a particular place. Thus, if a liver cell is needed, a stem cell can change itself into a liver cell. You could think about stem cells in various way. You could think of them as ‘blanks’, or as ‘general purpose’ cells. What matters is that they respond to the environment in which they find themselves and adapt as required. It may be, for example, that a stem cell in the liver, and at a place where a liver cell is required, is influenced by the surrounding liver cells, and caused by those cells to change into a liver cell.

But the precise mechanism is not important. What is important is that some organs of the body need loads more stem cells to replace dying cells, and it is in the more frequent mutations of stem cells that the possibility of rogue mutations are most likely to occur.

Without reading the actual detailed study (behind a paywall), it is impossible to know what the detailed evidence of the changes is. I think that it is reasonable to assume that there is actually real and detailed evidence. I can only quote the Summary:

VARIATION IN CANCER RISK AMONG TISSUES CAN BE EXPLAINED BY THE NUMBER OF STEM CELL DIVISIONS

Some tissue types give rise to human cancers millions of times more often [my emphasis] than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue’s homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to “bad luck,” that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes.”

I have bolded the phrase above because I was surprised by it. ‘Millions of times more often’? What does that mean? Is it referring to world-wide incidents of various cancers which are common, like breast and prostate cancer, as compared with extremely rare cancers? If these extremely rare cancers occur in places where there is little cell death and replacement, then it is easy to see how the researchers arrived at their conclusions.

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However, a strange happening has occurred. Somehow or other, CRUK, one week before the above study was published, published its own take on the subject. H/T Chris Snowden:

Life choices ‘behind more than four in 10 cancers’

More than four in 10 cancers – 600,000 in the UK alone – could be prevented if people led healthier lives, say experts.

Latest figures from Cancer Research UK show smoking is the biggest avoidable risk factor, followed by unhealthy diets.

Let us take that statement apart.

Life choices ‘behind more than four in 10 cancers’

More than four in 10 cancers – 600,000 in the UK alone – could be prevented if people led healthier lives, say experts.

Latest figures from Cancer Research UK show smoking is the biggest avoidable risk factor, followed by unhealthy diets.

Do you see? The ‘experts’ are not necessarily CRUK experts, and the ‘latest figures from CRUK’ are only figures which are quoted by CRUK.

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If it is true that CRUK has used this study for its own ends, then it has seriously misinterpreted (deliberately). The study DOES NOT say that ‘life choices’ are ‘behind more than 4 in 10 cancers’. It says that ‘more than 6 in 10 cancers ARE NOT dependent upon ‘life choices’. It does not provide evidence that ‘life choices’ cause the other third of cancers. The study makes no judgement on that issue. But I suppose that it could have indicated that cell apoptosis and replacement in the bronchial tubes ought not to be so frequent as to produce, randomly, the amount of cancer in those places as actually occurs in smokers. That is possible, but is still not ‘causation’.

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The statement:

“Two thirds of cancers are random due to ‘bad luck’, but one third is not ‘bad luck’, but, instead, is directly attributable to ‘life choices'”,

makes no sense when the evidence for ‘bad luck’ is so strong and the evidence for ‘life choices’ is so weak. The evidence for ‘life choices’ is weak because, a) it relies upon statistics (epidemiology) alone, and, b) because of the ‘age’ factor. The evidence for ‘bad luck’ (even as regards smoking and LC) is great, as shown in this graph:

img002

It is plain to see that some heavy smokers (the left-most line) were very unlucky, as were some moderate smokers, some light smokers, and some non-smokers, because they died before most of the other people alive at any specific time. Look at the non-smoker line (far right). Some non-smokers were unlucky and pegged out aged 45. More pegged out aged 50, and even more died aged 60. The rate of dying is not linear (a straight line), it is an acceleration (a curved line) as you can see. What is very noticeable is that, once the doctors started to die off in huge numbers (around the age of 60-70), all the doctors, whether smokers or not, started to peg out at the same rate. There is no doubt.

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The Hill and Doll ‘Doctors Study’ was undoubtedly a historic landmark. But, despite its long-term operation (1951 – 2001), there were, in that time period, and in the time period of some 50 years before the study began, enormous confounders. Many of the participants had survived WW1, with all its deprivations, gassings, shelling, etc. We should not underestimate the involvement of those doctors in WW1. What steps were taken to allow for that involvement? None that I know of. But the most curious thing was the lack of allowance for where the doctors lived and had their surgeries. For example, it seems to be true that, per 100 persons, there is far less LC for smokers of, say, 20 per day, who live in country areas, as compared with the equivalent persons who live in cities.

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I think that ‘The Tobacco Control Industry’ is like an army which has extended it lines and sources of supply way beyond what it can support. Yes, at the front, it will continue to have ‘massive successes’, but, in the rear, its supply lines will collapse.

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Regardless, the important thing is that we demand, demand, demand, to be left alone and that the persecution should stop. That is the most important thing. The persecution must stop.

 

 

 

 

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