
What causes cancer? It’s a simple question to ask, and – in so many ways – one of the hardest to answer.
And last week, as 2015 slowly got into gear and many of us put the finishing touches to our new year’s resolutions, some eyebrow-raising headlines appeared claiming that scientists had ‘proved’ that the answer is ‘mainly bad luck’.
This story came from a research paper from scientists at Johns Hopkins University in the US, (press released here). And it appeared to contradict the message that many organisations have been trying to hammer home (including us): that although there are no guarantees, we can stack the odds of avoiding cancer in our favour if we embrace a healthy lifestyle.
(In fact, just a week ago we published new stats showing how, if the UK’s population had been healthier overall, an estimated 600,000 cases would have been avoided over the last five years.)
We weren’t the only ones with raised eyebrows – a whole host of blogs and opinion pieces appeared over the weekend, scrutinising the claims. We’ll look at some of these criticisms below, and discuss why the research DOESN’T mean that two-thirds of cases of cancer are ‘caused by bad luck’ (whatever that means).
But before we do, let’s have a very quick recap of what the researchers did, and what they found.
The root of the story
The researchers set out to answer a simple but fascinating question: why do cancers arise more often in some tissues (e.g. the bowel) than others (e.g the brain)?
To try to answer this, they looked at what was already known about cell division rates in a given tissue (specifically, specialised cells called ‘stem cells’, which renew and replenish the tissues in our bodies) and how this related to the overall risk of cancer in that tissue.
‘The Stats Guy’ blog summarised it thus:
[T]he authors … looked at the published literature on 31 different types of cancer (eg lung cancer, thyroid cancer, colorectal cancer, etc) and estimated 2 quantities for each type of cancer. They estimated the lifetime risk of getting the cancer, and how often stem cells divide in those tissues.
They found a very strong correlation between those two quantities: tissues in which stem cells divided frequently (eg the colon) were more likely to develop cancer than tissues in which stem cell division was less frequent (eg the brain).
In other words, they found a mathematical relationship between the rate stem cells divide in a tissue, and the rate of cancer in that tissue (although several blogs questioned the way the researchers had used the statistics).
According to the researchers, the maths could explain two-thirds of the variation between different tissues.
It’s an interesting finding, which casts new light on an old mystery. But as Professor David Spiegelhalter noted on his blog:
“[This] may be a fairly reasonable statement to make about population rates in different tissues, but of course says nothing about variation in risks between individuals, and certainly does not say that two-thirds of cases are just luck.” [emphasis ours]
And that’s the key criticism of the way this paper has been interpreted. The media coverage has inadvertently jumped from talking about cancer rates in different tissues to speculating about cancer rates in the population. (Although it’s worth noting that the authors themselves still support the fact that certain cancers can be prevented by lifestyle changes.)
Other criticisms
The study also had another notable weakness: it looked only looked at cancer types where there was hard data about the rates of stem cell division.
As a result, they missed two of the most common cancers – breast cancer (which is influenced by lifestyle factors like a woman’s reproductive health, her weight after the menopause, and how alcohol much she drinks) and prostate cancer (which is only weakly influenced by lifestyle).
So although their finding is intriguing, there’s a way to go before we can say for sure it applies to all cancer types.
So where does ‘luck’ come in?

Molecular machinery of a dividing cell.
Let’s recap. Every time a cell in your body divides to create two new ones – something that happens billions of times a day – there’s a very (very) small chance a mistake could creep into its DNA, and one of the resulting cells could begin the long deadly journey towards developing into cancer.
And, as these researchers have shown, the more often a cell divides, the more chance there is of something untoward eventually happening.
So, in this sense, there’s an element of ‘bad luck’ about cancer. And it’s true that the disease can affect any of us – from the most avid gym bunny to the most determined couch potato.
But we also know there are a whole host of things that affect the chances of DNA damage developing in a dividing cell.
The chemicals in tobacco smoke, for instance, can modify DNA molecules, resulting in errors when they’re copied. The same is true of ultraviolet light.
And, similarly, things that change the rates of cell division over our lives will also influence the chance of a ‘bad’ cell division. For example, fluctuating hormone levels through puberty, periods, pregnancy and the menopause, can affect cell division rates in the breasts, womb and ovaries. Obesity too can influence our hormone levels, and thus cancer risk.
And long-term (‘chronic’) inflammation, as caused by certain infections, asbestos, and a host of other external influences, is thought to speed up cell division in other tissues.
(This is not an exhaustive list, just a flavour of the different things that can influence the development of cancer).
So to ascribe a particular patient’s cancer to ‘bad luck’ is essentially impossible. It’s a combination of myriad influences, some of which we can control, others which we can’t. And it’s certainly not about ‘blame’, as we’ve pointed out before.
In his response to the media stories, Professor Spiegelhalter had this excellent analogy:
[Imagine] there are tickets in a bucket marked cancers of different types, and a lot of blank tickets (and some marked ‘run over by bus’ etc). Smoking means you might get 20 times as many ‘lung-cancer’ tickets, but you still may be lucky and not draw one: many smokers don’t get lung cancer.
So chance plays a very strong role, even in so-called preventable cancers. This leads to the apparently paradoxical observation that most lung cancers are ’caused’ by smoking, while all lung cancers are also a matter of bad luck.
What about the media coverage?
It’s often tempting to blame ‘the media’ for mangling science stories, but, as is often the case, there’s a more complicated story here (one that the excellent 2020 Science has dissected in full).
But this isn’t about pointing fingers. It just seems a huge shame that something that is, as far as these things go, established scientific fact – that cancer rates are affected by lifestyle – has been called into question.
For those that doubt the effect these stories can have, just read this tweet:
THANKYOU BBC!! Smoking doesn’t cause cancer. It’s just bad luck
— Kevin Unwin (@kevounwin) January 2, 2015
One of the gratifying things about this story was the speed with which other voices all over the Internet shone a spotlight on the story even before the day was out. So we’ll leave the final word to Adam over at The Stats Guy blog:
We often see medical research badly reported in the newspapers. Often it doesn’t matter very much. But here, I think real harm could be done. The message that comes across from the media is that cancer is just a matter of luck, so changing your lifestyle won’t make much difference anyway. We know that lifestyle is hugely important not only for cancer, but for many other diseases as well.
For the media to give the impression that lifestyle isn’t important, based on a misunderstanding of what the research shows, is highly irresponsible.
– Henry
References
- Tomasetti C. & Vogelstein B. Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions., Science (New York, N.Y.), PMID: http://www.ncbi.nlm.nih.gov/pubmed/25554788
- Black cat image via Istolethetv/Flickr, used under a CC-BY 2.0 license
Comments
Kate Elliot January 8, 2015
Some cancers may indeed be caused by lifestyle, but to those of us that have had it, yet have always lived a healthy lifestyle and are surrounded by people who don’t look after their bodies, it really is bad luck; although my choice of language would be slightly different under normal circumstances. I was 17 when I first had cancer, then 40 when I had it again as a result of the treatment I had when I was a teenager. I have got through it, and I do think, as others have said, that my healthy lifestyle, and attitude has helped me get through it, but I think even survival sometimes is luck, not necessarily down to the individual’s lifestyle. I was an active and healthy child and teenager; there was nothing I did that caused it. I grew up with 3 other siblings who all shared the same environment, ate the same food and behaved in the same way I did and none of them have developed cancer, and I hope they don’t. It was random, bad luck. Children and teenagers who develop cancer do not develop it because of their ‘lifestyle choices’. While I think that to dismiss the theory that some cancers are affected by lifestyle is short-sighted, I too believe that not enough is made of the fact that sometimes it just happens. It just does; and that is very bad luck.
Anne January 8, 2015
While I am in total agreement with encouraging a healthy lifestyleand, as such, I have always led a healthy lifestyle myself, I was recently diagnosed with colon cancer. I have never smoked, I drink in moderation, exercised regularly and always eaten healthily. When I look at causes of colon cancer on cancer information websites, I feel it is a stigma against me and people who don’t know me will presume I lead that kind of lifestyle. I don’t think all cancer is down to bad luck but I do think that scientists need to keep an open mind in all this. I am sick of feeling like the bad person for having cancer.
Ruth Loft January 8, 2015
P.S. to my earlier blog.
A healthy lifestyle is essential for all of us all the time so that if disaster strikes, in the form of cancer or other diseases, recovery from surgery and chemical treatments will be faster.
Ruth Loft January 8, 2015
As someone who has had breast cancer twice I am convinced it is just down to luck. (apart from the genetic 15 per cent). I have always said there is no rhyme or reason to it. On the other hand I know smoking causes lung cancer and lifestyle, diet, weight, exercise etc. are contributory factors in other cancers. I have run a support group for ten years for ladies who have been diagnosed with breast cancer so am quite confident in my views. I have seen hundreds of ladies through our group over the years who have been sensible enough to spot breast problems early or take advantage of screening. Early diagnosis is essential in treatment and prognosis.
Penny Lapish January 8, 2015
It’s nice to see the whole picture being given in regards to cancer. Unfortunately having had breast cancer and not having been a smoker, drinker or overweight it was difficult for me to accept my diagnosis…I’d tried hard to live a healthy lifestyle.
Thanks Cancer Research for setting the story straight!
Trudy Allen January 8, 2015
My mother died of lung cancer, though she didn’t smoke. I had a grandmother who smoked for 40 years and died at 103 of old age. Whilst living a healthy life is no guarantee that we won’t get cancer, there are clearly lifestyle choices which we all know raise the risks. I have smoked, sunbathed and drunk too much when I was younger, but as I have grown older appreciated the greater risk I am putting myself at and have chosen to modify my behaviour accordingly. I can’t undo the damage I’ve already done, but hopefully I have prevented further damage. It is not about blaming someone for doing any of these things but making sure we all appreciate that if we don’t cut down or stop then we are putting ourselves at an increased risk of getting cancer.
Marilyn Wood January 8, 2015
I agree with a lot you have said on your blog but not all of it, I have always led a very healthy life style, I go to the gym twice a week to do yoga, I walk 4/5 times a week for 25mins, I don’t smoke or drink & eat lots of fruit & vegetables, I am 58 & in my menopause my BMI is 23 & I weigh 53.4k & I have taken HRT for the last 8 yrs, I have just been diagnosed with breast cancer so maybe it was a bit of back for me due to the HRT although I know people who have never taken HRT and not had breast cancer but this has not stopped me from continuing to lead a healthy lifestyle
Neville Forrest January 8, 2015
I feel the person or persons responsible for press release saying cancer was down to luck have behaved irresponsibly .
Over recent years great steps have been made in the cure rates for many cancers and there can be little doubt that healthy living plays a major part in this
Of coarse genetic related cancers can be considered bad luck.
But we should keep faith in cancer research it plays a major roll all around the world
Karen Marlowe January 8, 2015
Sorry but go hang out in a cancer support group and you will find many there that lived healthy lifestyles and have cancer. They are also the angriest of patients because they have been told a healthy lifestyle protects them.
Maureen Walker January 8, 2015
I have always been upset by the inference that when people get cancer it is their own fault,my husband did not smoke ate a very healthy diet but got cancer,my niece is a nurse but still got ovarian cancer at 33,I am liable genetically to get colon cancer,should I feel guilty?Also being brave does not help to fight it
David Haughton January 8, 2015
it’s all in the detail as usual – not the misleading headlines. Keep up your good work!
Maggie Walsh January 8, 2015
I have to agree with Elizabeth Willis to some extent. I am sick and tired of being made to feel guilty about having had cancer. It is bad enough dealing with it and living with its consequences without being told all the time that healthy living may have prevented it. Yes, I might have avoided smoking in my younger years had I been given better information, yes, I know alcohol could be a contributing factor, yes I know I should do 150 mins of exercise a week, yes, I know the strong sun should be avoided. I could go on and on. I do try to keep healthy and follow all the guidelines, but I do slip from time to time. And do I feel guilty? YES, but I am human and I do want to sometimes enjoy myself in the time I have got left, that is until I get the next cancer or reoccurrence because I had one too many glasses of wine last week and only managed a 30 minute walk.
Finally, how could healthy living have helped me control my hormone levels? The “bad cell division” that led to my breast cancer may have been influenced by fluctuating hormones. What could I have done to help prevent this?
Sharen Hassall January 8, 2015
I was surprised by these headlines myself after research undertaken previously has suggested we all need to lead healthier lifestyles in order to avoid cancer.
However, having been diagnosed with breast cancer myself almost four years ago, I was particularly upset at the time of diagnosis by media suggestions that breast cancer is caused because women are obese, unfit, don’t exercise enough & basically lead unhealthy lifestyles. At the time I was undergoing chemotherapy there seemed to be a lot in the media & on the news to suggest this had been evidenced from research which had been undertaken. I am & have never been in the slightest bit overweight, I’ve never smoked, I enjoy a couple of glasses of wine with a meal at the weekend (although this is rare these days after other research has suggested even one glass of wine can increase the chances of breast cancer returning if you have had it in the past). I exercise regularly, participating in yoga, pilates, zumba & aerobic type classes & as soon as I recovered from major surgery I went straight back to these classes as another research project suggested women can reduce the chances of breast cancer returning by keeping up or increasing the level of exercise undertaken. I walk whenever I can as opposed to using the car & will take the stairs as opposed to using a lift if possible; I even walk up escalators rather than stand & wait to arrive at the top!
Whilst I was feeling ill with the effects of chemotherapy I remember wanting to scream at the TV that they needed to make the point that not ALL women who contracted breast cancer fell into this category.
Because I believe I’ve led a healthy lifestyle & there is no family history of breast cancer, I like to think that I’ve just been ‘unlucky’. However, I also very strongly believe that being so fit & healthy is what helped my recovery from both surgery & chemotherapy. So, I can see both sides of the argument, I just wish it could be made clearer sometimes by the media that not all of us breast cancer survivors are or have been fat couch potatoes abusing our bodies by smoking & stuffing all the wrong foods into them!!
I’m going to put my hands up and say that when I read the news that ‘two thirds of cancer cases were bad luck’, I believed it. it made me doubt trying to have a healthy lifestyle and I feel like lots of people will have taken on board this news, just as in the tweet above, and will continue to do harmful things to their body thinking ‘hey, if its all bad luck anyway then screw it!’.
Great article and thank you for clearing that up. There is luck/ chance in every aspect of life and this applies to cancer too, however its refreshing to know that a healthy lifestyle still counts.
Ruth King January 8, 2015
Thank you for writing this. I read the article which was published by various news providers with dismay, as I and those I love (and I’m sure many more), try very hard to lead a balanced and healthy lifestyle, with the hope that it helps contribute to a good quality of life and also a reduced chance of getting terrible diseases like cancer. I’m glad that the message isn’t quite as clear cut as these articles made it appear. I hope that others don’t just give up after reading those articles!
E Harrison January 8, 2015
Excellent blog and much needed after the stupidly mistaking headlines last week! Great work as ever from all involved.
Matthew January 8, 2015
Henry, very sensitive response to Elizabeth’s comment. Excellent science and excellent communication!
Stephen Walker January 7, 2015
There is no mention of children’s cancer here?
Anne January 7, 2015
Shouldn’t we also be promoting the message that if you are ‘unlucky’ enough to be diagnosed with cancer, being fit and having a healthy lifestyle may aid your recovery and help you withstand treatment?
Henry Scowcroft January 7, 2015
Elizabeth,
Thanks for your comment. We’re truly sorry to hear about the impact cancer’s had on your family. It’s never our intention to annoy or upset anyone – particularly anyone affected by cancer – and we apologise if we’ve done so. Our reason for writing the article was to highlight the fact that, in some cases, cancers are influenced by lifestyle factors such as smoking. Of course, in others, these factors play no part at all. And whether lifestyle factors could be linked or not, cancer is never someone’s fault. But we were concerned about the way the media covered the ‘bad luck’ story, and how it clearly led some to believe that lifestyle factors play no role at all (for example, in the tweet embedded above). It’s a really tricky balance to strike, there’s an element of luck or chance to most things in life. But we need to keep talking about things like smoking, obesity, physical activity and the rest, because the evidence shows that parts of our life that we can influence, like these, play a large part in the UK’s overall cancer rates (see, for example, this story).
But that’s not to say we ever want anyone to feel ‘blamed’ for their disease – cancer is never anyone’s ‘fault’, and we wrote an article a while ago addressing this very point, which you can read here:
http://news.cancerresearchuk.org/2012/04/11/lifestyle-and-cancer-against-the-blame-game/
Thanks again for your comment, and for your support over the years – it means a lot to us. And, once again, please accept our apologies for upsetting you or anyone else. We wish you all the best,
Henry
Cancer Research UK
Elizabeth Willis January 7, 2015
You have annoyed a lot of cancer sufferers. I was diagnosed with breast cancer 1 year ago, I don’t smoke, used to row and work out regularly etc. My son was 4 when he was diagnosed with a brain tumour, my sister had leukaemia, her husband colon cancer, my ex had non-Hodgkin’s lymphoma . I think we are extremely unlucky as we are all theoretically fit; my son studies human bioscience and he was not at all surprised by the news. I support CRUK by monthly donations by the way (£50 by GAYE). I think you should support the news as many people are made to feel guilty about their illness and it really made me feel better when this news came out. I wasn’t so happy when I saw this.
Aaron Meyer January 6, 2015
The interpretation of this study is based on a frightening variety of errors in interpretation and basic math. http://ameyer.me/science/2015/01/02/vogel.html
Jim Woodgett January 5, 2015
Great balanced summary of the reactions to the press release and press reports. It’s easy to see how this was twisted – most people do not understand relative versus absolute risk and the methods used intros paper push limits of statistical analysis.
I do think there is one area of value to the reporting of the finding, even if it only reiterates what Richard Doll and others have espoused for many years, in that random chance does play a significant role and there is no reason for victim-blaming. This is important as many newly diagnosed patients feel guilty that they have somehow contributed to their disease when this is impossible to tell (and is probably not the case). This is countered somewhat by the message that “it’s out of my hands so I can do what I like”. Obviously, that isn’t the case and such people are unlikely to act on any evidence (such as the 18 fold higher risk associated with smoking and lung cancer).
b ane gader January 8, 2015
I cannot get over the selfish quote of K Unwin.Surely its no better to smoke at other innocent people than it ever was.Just because you may not get cancer with every cigarette containing 4000 chemicals other people ‘non’smokers dont want to breathe all those toxins in, asthmatics the frail the weak. the ill.When will society keep smoke in designated areas away from those who at the moment have not got a choice but to breathe foul toxic air in just to go shopping or to the opticians.Smoke gets in your eyes and in everypart of the body which is fine for those who choose that but what about rights health rights for those who dont.People may have liver and kidneys working double hard for other reasons they dont want to breathe nicotin bitumin and all the other unknown ingredients in.Stick to breathing in cigarette fumes in places like your own home garden where other pedestrians dont have to take you fall.