Cancer: Misinformation is a risk factor too

People who know me personally will know that I don’t take cancer lightly (for various reasons I won’t go into here). So I am always a bit reluctant to criticize people who make the fight against cancer their life’s mission. After all, there are easier jobs. But cancer is not just a physical illness; it’s also a taboo-laden, paranoia-attracting, terror-inducing cultural obsession. And that means that most people’s understanding of it will be a product of much more than merely reliable information and sound judgement. A whole lot of psychology will be in the mix too.

That’s why professional cancer docs need to be especially careful when communicating information to the general public. Ditto mainstream intellectually-driven news media. At this stage, some newspapers (such as the Daily Mail) are such laughing stocks in the world of cancer hysteria (Ben Goldacre famously described them as being “on an ongoing ontological program to divide all inanimate objects into ones that will either cause or cure cancer“), it is difficult to read their cancer stories with a straight face (see here and here). Other newspapers, such as the Guardian, (probably) deserve to be taken more seriously.

But, when it comes to medical scares, even the Guardian can play with fire now and again. Today’s piece on cancer, while mostly wholesome, might just be a case in point.

Click to see a hard-hitting comment on cancer at (contains swearing)

The lengthy feature is called The Insiders’ Guide to Cancer Prevention. It comprises short contributions by six different cancer experts, purportedly aiming to describe ways of preventing six different classes of cancer (you know: the lung specialist tells you to avoid smoking, the neurologist advises taking a daily aspirin; that type of thing).

As I say above, it is difficult to criticize such efforts, especially when there is a stated attempt to provide advice that is based on scientific evidence. But in truth, the advice here is based more on expertise than on evidence. While there are certainly references to the research literature, there is more than a small dollop of anecdotal reasoning and appeals to personal experience. Opinion, in other words. The opinion of highly regarded people, yes, but opinion nonetheless.

I like to call this type of thing “Eminence-Based Medicine” (in fact, as I’m quite proud of that one, you can read it as Eminence-Based Medicine).

A certain amount of personal stuff is fine, I suppose, if only to establish rapport with lay readers. But sometimes it can be difficult to tell where the facts end and the opinions begin. And sometimes opinions can be, well…plain crazy.

Old news

Here’s an example of the blurriness problem. When discussing breast cancer, the expert refers to studies that question the usefulness of breast cancer screening:

Just this week the papers splashed on another piece of research criticising breast cancer screening, saying that for every woman saved by the procedure, up to 10 have been treated unnecessarily.

The news story in question refers to a recent Norwegian study which found that breast screening leads to widespread over-diagnosis of cancers. But it should also be noted that this is by no means a new finding. In fact, it is merely the latest corroboration of several other previous studies that have found exactly the same thing.

The problem is the number of women who receive ‘false positive’ test results, women who are told they have cancer when in fact they do not. When screening programmes are studied around the world, these women — who often then undergo unnecessary cancer treatments — appear to far outnumber those who benefit in terms of having their lives extended.

This is basic information for those professionals who specialize not in cancer, but in scientific literacy. Indeed, the UK-based advocacy group Sense About Science have produced this pamphlet attempting to promote a sophisticated understanding of the nuanced cost-benefit analysis that is necessary when considering screening of various kinds.

Click above to access the Sense About Science pamphlet

But what does the Guardian’s breast cancer specialist make of it all?

This sort of coverage is a constant annoyance…

Oh, that pesky research literature and its mountain of empirical data! Oh, the consistency of its findings!

…The evidence just doesn’t stack up…

I beg your pardon?

…I’ve worked as a breast surgeon for 16 years, and have been having mammograms myself since I was 44, six years younger than the NHS breast cancer screening programme stipulates. To my mind, it is still the strongest preventative measure one can take…

Oh, I see. When you say “the evidence just doesn’t stack up“, what you mean is “the evidence doesn’t tally with my personal judgement“. Well, I’m afraid that’s just too bad. The latest Cochrane review has clocked data from nearly one million women and found that 10 times more received unnecessary treatment than actually benefited.

Yes, breast cancer screening saves lives (for around 1 woman per 2,000 across a decade). But it also hurts some women (around 10 per 2,000 across a decade). And there is quite a lot of evidence on this issue which does stack up quite nicely, thank you — so much of it in fact that to dismiss it on the grounds of personal experience is a little distasteful, even from a cancer specialist.

The issue provides a nice example of how good intentions can sometimes cloud scientific judgement. We’d all love to be in a world where cancer screening carried only benefits and no costs. But I would expect that part of the job of being a cancer specialist is to ensure that potential patients are made intelligently aware that we do not live in such a world.

Dodgy homeopathy advice ahead: Not efficacious, you’ll understand, but maybe able to…prevent cancer?

So what about the plain crazy stuff I mentioned earlier? Well here you go. Here’s the Guardian’s expert on colorectal cancer:

Nor am I one to dismiss leftfield practices outright. As well as surgery and screening, I have research interests in prevention, and have seen projects on all manner of quirky methods. If people wish to use homeopathic medicine in an attempt to prevent cancer, despite there being no medical evidence for its success or any active component whatsoever, the placebo effect itself may be strong.

So, okay, on the one hand, the guy notes that “there is no medical evidence” for the usefulness of homeopathy in cancer prevention (someone should tell the homeopaths about this). However, “the placebo effect” may be strong. There is no other way of reading this statement except to conclude that this particular cancer specialist — an expert — believes that the placebo effect can prevent the onset of cancer.

Let me put this simply. There is absolutely no evidence anywhere that placebo processes can influence biological processes relating to cancer onset, progression, or recovery. None. Nada. Zilch. It ain’t there.

Placebos can be helpful in moderating the experience of symptoms (such as pain and nausea) associated either with the cancer itself or with treatments such as chemotherapy. But such effects do not affect the actual cancer per se.

I respectfully suggest that this particular doctor might know his onions when it comes to colorectal cancer, but he certainly butters no parsnips when it comes to placebos.

Alternative English glam-rock doesn’t prevent cancer either

When it comes to cancer, awareness is often a key determinant. It is correct that cancer doctors should get out there and help people to become informed about what cancer is, what treatments for cancer actually look and feel like, what cancer is caused by, and what we know about how to prevent it.

Taking on the task of informing the public about cancer assumes that spreading information is actually a good thing. It also surely implies that spreading wrong information is not so good. Unfortunately, while the Guardian piece is positively informative in lots of respects, the two problems described above are huge distractions.

It’s good to know that cigarette smoking, physical inactivity, red meat, and so on are risk factors for cancer. But another huge risk factor is misinformation about cancer. To be taken seriously, articles offering advice on cancer prevention just simply cannot have any.

Otherwise, we might just as well go back to reading the Daily Mail.

At least it’s funnier.

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  1. The new colour theme makes this article impossible to read.

  2. Wait nevermind! Refreshed and it’s fine again. May have been my laptop

  3. Pingback: April | Pearltrees

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