By Andy Ho, Senior Writer, The Sunday Times, 18 Jan 2015
Many people may have been shaken by a study just published in the top journal Science that was reported to have discovered how two-thirds of all cancers were simply due to "bad luck", about which you can do nothing.
This was a Johns Hopkins study which reported that 65 per cent of cancers are caused by mutations that emerge randomly, unpredictably and spontaneously during cell division. That's a majority of cancers. So you can't do a thing to prevent most cancers.
This was a Johns Hopkins study which reported that 65 per cent of cancers are caused by mutations that emerge randomly, unpredictably and spontaneously during cell division. That's a majority of cancers. So you can't do a thing to prevent most cancers.
Hopefully, people did not just read the headlines to conclude that smoking is not so bad after all or we can all gorge on red meat, drink to our heart's content, forget the jogging and lie in the sun as much as we want.
The media did not misreport what the Johns Hopkins communications department put out. The hullabaloo that ensued made its publicists issue a clarification in the form of a Q&A with the researchers.
There was no misreporting but many had played up the "bad luck" - a term used once in the paper's abstract itself.
But don't get too excited, and don't stop heeding the good advice on how to avoid cancer.
The study actually did not tell experts anything they did not already know, though most ordinary people may not have been aware that most cancers cannot be prevented.
So what did the study find and what is its value?
It reported that 65 per cent of cancers are caused by mutations that emerge randomly, unpredictably and spontaneously during stem cell division.
It reported that 65 per cent of cancers are caused by mutations that emerge randomly, unpredictably and spontaneously during stem cell division.
The stem cells found in people - not embryos - are called adult stem cells. They are blank slates that generate the type of cells that make up the specific type of tissue in which they reside. For instance, adult stem cells in the bone marrow develop into the various types of blood cells that are found in the blood stream.
Mutations are errors in DNA replication when cells divide. Mutations in stem cells lead to cancers developing because they can alter the manner in which stem cells develop and grow.
Under normal conditions, cell division is controlled and orderly as there are intricate regulatory mechanisms to keep cells from replicating wildly and growing out of control. But mutations can disable such control mechanisms, and the stem cells involved will proliferate wildly to develop a cancer.
These mutations arise randomly as stem cells replicate to replace human tissues that grow old and die off. These are different from mutations people inherit from their parents. Inherited mutations probably cause only up to 10 per cent of all cancers.
Environmental factors are the third main cause of cancers - and these are the ones that are potentially preventable through lifestyle choices.
Logically, there are more opportunities to develop mutations the more times a cell divides. In this study, the researchers calculated what the stem cell division rate in a particular type of tissue would predict its cancer rate to be.
Say the division rate of stem cells in lung tissue was A and this works out mathematically to cause a cancer rate of Z. The division rates for different tissues were calculated and then what cancer rates these would lead to were also worked out. These predicted rates were then compared to their known cancer rates in the real world.
It was found that the predicted cancer rates matched real cancer rates closely. This means that cancer rates are largely explained by spontaneous mutations occurring during cell division.
The study concluded specifically that two-thirds of cancers are caused by these unavoidable, random mutations that are intrinsic to cell division for tissue replacement, the very thing that sustains life itself.
So most cancers are not due to environmental factors or inherited genes. The former, like exposure to sunlight or smoking, can in theory be avoided as lifestyle choices whereas the latter may be prevented only if patients do not have children.
And it follows that if we could wave a magic wand to remove all environmental toxins and inherited mutations, many would still have cancer because it is generated intrinsically.
So there is a minimum rate of cancer just from our being human - and most cancers can't be prevented.
Scientists have long known that some cancers are "random", which was why they found it hard to understand why this "news" about cancer and "bad luck" was so disturbing for the layman.
It may be that people dislike being told that they can do their darndest to stay healthy but random mutations may get them anyway.
Perhaps we would rather hear that most, if not all, cancers can be prevented if scientists understand cancer biology thoroughly and could tell us what causes all cancers.
The Johns Hopkins study reinforced the fact that chance can play a big role in determining who gets a mutation that leads to cancer. It may be hard to accept, but for a lot of cancers, the cause is unpreventable random mutation.
So why bother to publish a study that says nothing really new?
So why bother to publish a study that says nothing really new?
Well, it is another bit of evidence that cancers are largely a "bad luck" affair. Science progresses by the accumulation of evidence from different groups of scientists working independently.
And it is the first time that someone has crunched some data to give some precision to generally accepted expert guess-estimates that the causes of cancer are environmental, intrinsic mutations and inherited mutations in 30 per cent, 30 per cent and 10 per cent of cases in that order, with the remainder being a combination of two or all three factors.
Could the Johns Hopkins people have explained their research better?
It is always difficult to parse complicated science for the public, so a publicist would be hard-pressed to not resort to short cuts and buzzwords.
When all is said and done, this study doesn't change the correct advice to live right to prevent some preventable cancers.
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