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Bad luck and cancer – did the media get it wrong?

Andrew Maynard

Risk Science Center

January 03, 2015

The chances are that, if you follow news articles about cancer, you’ll have come across headlines like “Most Cancers Caused By Bad Luck” (The Daily Beast) or “Two-thirds of cancers are due to “bad luck,” study finds” (CBS News).  The story – based on research out of Johns Hopkins University – has grabbed widespread media attention.  But it’s also raised the ire of science communicators who think that the headlines and stories are, in the words of a couple of writers, “just bollocks”.

With all the coverage of the paper, and the subsequent coverage of the coverage, I was interested in just how off-base the news articles were, and to what extent this was down to lazy reporting.

The paper in question is “Variation in cancer risk among tissues can be explained by the number of stem cell divisions” by Cristian Tomasetti and Bert Vogelstein, published this month in the journal Science.  At the heart of the paper the authors look at how stem cell divisions in different tissues correlate with lifetime risk of developing cancer in those tissues.  The study shows a clear correlation with the cancer types considered – the faster the stem cells divide in a particular tissue, the greater the chance of developing cancer in that tissue.

‚ÄčThe two researchers then tease out the degree that they think random genetic mutations, as opposed to environmental and lifestyle factors, influence cancer risk.  They conclude that, out of 31 cancer types considered, 22 were primarily associated with random genetic mutations (they called these “R-tumors” – the R standing for “random”), and nine were associated with environmental factors on top of these random mutations (deterministic tumors, or “D-tumors”).

In the author’s words,

“We refer to tumors with relatively low ERS [“extra risk score”] as R-tumors (R for replicative; green cluster in Fig. 2) because stochastic factors, presumably related to errors during DNA replication, most strongly appear to affect their risk.”

In other words, out of the 31 cancer types studied, the authors’ analysis showed that 70% of them – just over two thirds – were predominantly determined by random mutations and not environmental factors; what the authors term in the paper as “bad luck”.

The inference that many cancers – and even cancer types – cannot easily be prevented by reducing environmental exposures or changing lifestyles, proved to be a media-magnet.  Headlines resulted along the lines of

“Cancer Is More Bad Luck Than Bad Behavior, Study Says” (Bloomberg)

“Two-Thirds of Cancer Cases Are Simply Down to Bad Luck” (Gizmodo)

“Two-thirds of adult cancers largely ‘down to bad luck’ rather than genes” (The Guardian)

“Most cancer types ‘just bad luck'” (BBC News)

“Most cancer cases ‘due to bad luck'” (Daily Mail)

And some commentators weren’t amused.

Michael Head for instance tweeted

In response to many of the headlines and articles, Adam Jacobs (linked to in the tweet above) wrote on his blog The Stats Guy

A paper published in Science has been widely reported in the media today. According to media reports, such as this one, the paper showed that two thirds of cancers are simply due to bad luck, and only one third are due to environmental, lifestyle, or genetic risk factors.

The paper shows no such thing, of course.

… concluding with

We know that lifestyle is hugely important not only for cancer, but for many other diseases as well. For the media to claim that lifestyle isn’t important, based on a misunderstanding of what the research shows, is highly irresponsible.

Over at The Guardian, the media-questioning was taken up by Bob O’Hara and GrrlScientist under the headline “Bad luck, bad journalism and cancer rates”.  Not pulling their punches, they wrote:

The big science/health news story this week is about cancer rates, with news outlets splashing headlines like “Two-thirds of adult cancers largely ‘down to bad luck’ rather than genes” (for example, here) or “Most cancer types ‘just bad luck’” (here). (I’m not even going to look to see what the Daily Mail has to say about this.) But these headlines, and the stories, are just bollocks. The work, which is very interesting, showed no such thing.

At this point my curiosity was piqued (egged on my science bloggers like Ed Yong who similarly questioned the media coverage). Was this just a particularly egregious case of widespread lazy journalism, or did the stories have a common root?

Reading the original paper, the authors were clearly building a case for the majority of the cancers they studied having predominantly random origins.  This is particularly clear in figure 2 in the paper (which should be viewable here) where they cluster cancers into random versus deterministic types.  But the language is still somewhat cautious in the paper.

The associated press release from Johns Hopkins University is more direct.  Under the headline “Bad Luck of Random Mutations Plays Predominant Role in Cancer, Study Shows”, the press release states

“By [the authors’] measure, two-thirds of adult cancer incidence across tissues can be explained primarily by “bad luck,”

At this point, the press release is referring to the role that random events play in determining whether a cancer will develop.  As the release clarifies,

Using statistical theory, the pair calculated how much of the variation in cancer risk can be explained by the number of stem cell divisions, which is 0.804 squared, or, in percentage form, approximately 65 percent.

In other words, they conclude that random genetic mutation “bad luck” as stem cells divide is an important factor underlying the numbers of cancer cases observed – and as a result the lifetime risk of developing cancer.

The release goes on to note:

Finally, the research duo classified the types of cancers they studied into two groups. They statistically calculated which cancer types had an incidence predicted by the number of stem cell divisions and which had higher incidence. They found that 22 cancer types could be largely explained by the “bad luck” factor of random DNA mutations during cell division. The other nine cancer types had incidences higher than predicted by “bad luck” and were presumably due to a combination of bad luck plus environmental or inherited factors.

This directly mirrors the findings presented in the paper; that of the cancers studied, 70% were largely explainable by random mutations during cell division.

Comparing this to the headlines above, the media articles, release and paper align surprisingly well.  “Bad luck” is the authors’ phrase, and they do emphasize the dominance of random genetic events in the majority of cancers, and cancer cases.

In this respect, it’s hard to be too tough on on the media coverage – sure, some of the stats may have  got a little twisted, but the dominant message seems to have its roots in the paper and the institutional (and author-sanctioned) press release.

So is there a problem here, or have the media actually done good, contrary to perceptions from some quarters?

From my reading of the paper, the press release and the media coverage, this isn’t as straight forward as it might seem. Certainly, it seems that many reporters made an honest effort to faithfully represent what the authors were saying.  And yet, science reporting is more than just reporting the facts – it’s also contextualizing those facts in a way that is useful to readers and society more generally.

Going back to Adam Jacobs’ piece, it’s worth repeating his conclusion:

We know that lifestyle is hugely important not only for cancer, but for many other diseases as well. For the media to claim that lifestyle isn’t important, based on a misunderstanding of what the research shows, is highly irresponsible.

If you take the stance – as he does – that environmental and lifestyle factors are critical to determining good and bad health (and as a public health professor, its a stance I am professionally expected to take), news articles that imply we don’t need to worry so much about the pollution we emit, the chemicals we expose people to or the way we live our lives, can be seen as highly irresponsible unless backed up by rock solid evidence.  They open the door to an abdication of responsibility when it comes to environmental health.  Why spend a fortune on preventing environmental emissions when they don’t matter? Why undergo cripplingly expensive product safety testing if ingredients don’t really cause cancer?  Why support inconvenient regulatory agencies if all they do is cripple commerce without preventing cancer and other diseases?

This is a valid fear, backed up by a long history of environmental health disasters.  And it’s a fear that requires researchers and research institutions to take at least some responsibility for how they pitch and promote their work.

In the case of this paper, it’s hard to see clear evidence of bad reporting.  There is a lack of balance and contextualization though that, it seems, has its roots in the original paper.

This is not a criticism of the paper.  But it’s very easy for the significance of research that begins to challenge the status quo to be inappropriately amplified in the media. As I noted in a recent article in Nature nanotechnology,

“when surprising new insights emerge on possible material health risks, where does the responsibility lie for ensuring that new research is conducted on material safety, without this research influencing consumers and regulators before there is plausible justification for action? Or to put it more succinctly, how can we encourage exploratory risk research without it prematurely impacting consumer and regulatory decisions?”

This refers to research on engineered nanomaterials, but the point is just as relevant here: it’s extremely easy for exploratory research to take on the aura of authoritative, actionable knowledge through the lens of the media.

So where does responsibility to temper such amplification lie?  Clearly there needs to be responsible reporting at every point in the communication chain.  But by the very nature of amplification, care is needed at the source of a story to help ensure that the final reporting is both accurate and responsible (an issue I look at more closely here)

In this case, it was perhaps inevitable that research indicating environmental factors may not be as important as previously thought in causing cancer would lead to “just bad luck” headlines.  But those headlines draw explicitly on the language used in the paper and the press release.

Would the media coverage have been different if the work was pitched differently?  It’s hard to tell – but in this instance I’d certainly be hesitant to put all the blame on bad journalism.

Paper: Variation in cancer risk among tissues can be explained by the number of stem cell divisions (2015) 
Cristian Tomasetti and Bert Vogelstein. Science, Vol. 347 no. 6217 pp. 78-81 DOI: 10.1126/science.126082

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Andrew Maynard is Director of the Risk Science Center at the University of Michigan School of Public Health.


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