More awful reporting from the BBC about breast cancer

Michelle Roberts of the BBC has produced a wholly misleading report about a study of sex hormones and breast cancer risk based on a press release from Cancer Research UK. It's a 38% cut and 45% paste job according to churnalism.com. It's a shame it's not 100% cut 'n' pasted because although CRUK rather glorified the study, their press release was at least factually accurate.

The Beeb's version is this:

Obesity 'leading driver' of breast cancer

Obesity is the biggest driving force behind the most common form of breast cancer in older women, say researchers.

Alcohol and then cigarettes are the next largest culprits, according to Cancer Research UK.

This follows the well-worn path of blaming food, alcohol and tobacco for every disease known to man, which is presumably why the Beeb reported it. But this conclusion is in no way borne out by the study itself or even Cancer Research UK's press release. Obesity and drinking are moderate risk factors for breast cancer and the balance of evidence suggests that smoking is not a risk factor for breast cancer at all.

The best advice that could be given to women to avoid breast cancer is to have children early in life and have lots of them. This, however, doesn't fit into the sin = death narrative of our times and so the usual lifestyle factors must be trotted out.

If you look at CRUK's list of risk factors for breast cancer, you will see that obesity and alcohol feature a long way down and that the charity concedes that the weight of evidence, including an IARC monograph, shows that smoking is not a factor.

How then, does the BBC conclude that obesity is the number one 'driving force' for breast cancer, closely followed by alcohol and smoking? The answer is that, once again—and in common with the Daily Mail—Beeb reporters simply can't read a scientific study properly.

The paper in question looked at risk factors for high concentrations of sex hormones in postmenopausal women which, in turn, is one risk factor—though not the main one—for breast cancer. They found a reasonably strong correlation with weight and rather more modest correlations with drinking and smoking. The researchers don't claim that these factors are the main cause of sex hormone concentrations, let alone of breast cancer itself. The researchers also note that most studies have found no link between smoking and breast cancer.

In other words, the BBC has completely misinterpreted the study. It's not the worst health reporting I've ever seen, it's just routine incompetence that will mislead many thousands of women.

I wrote to the BBC earlier today about this, but as I entertain no hope of receiving a reply, I'll reprint what I said here:

Dear Michelle,

Your report today about sex hormone concentrations fundamentally misrepresents the study in question. It begins:

"Obesity is the biggest driving force behind the most common form of breast cancer in older women, say researchers. Alcohol and then cigarettes are the next largest culprits, according to Cancer Research UK."

This is not what the study says at all, nor is it what the Cancer Research UK press release says:

"Weight is the biggest factor affecting the level of sex hormones that increase breast cancer risk in post menopausal women, according to new research published in the British Journal of Cancer today (Wednesday)."

There is a crucial difference between these two statements. Sex hormone concentrations are one risk factor, though not the main one, for breast cancer. The study in question looks at three possible risk factors for higher sex hormone concentrations and finds a reasonably strong relationship with weight and more modest relationships with alcohol and smoking. The study does not say that these three factors are the main contributors to sex hormone concentrations and it certainly does not say that they are the three main risk factors for (or 'driving forces' of) breast cancer itself.

The main risk factors for breast cancer, as stated on Cancer Research UK's website, are age and reproductive history. There are moderate associations with obesity and alcohol, but the weight of evidence shows that smoking is not a risk factor at all. In reference to smoking, CRUK states: "In 2004, the International Agency for Research on Cancer concluded on the basis of the existing evidence that smoking and secondhand smoke do not cause breast cancer". This is also stated in the study you reported on today:

"Most epidemiological studies have suggested that smoking has little or no effect on breast cancer risk (Collaborative Group on Hormonal Factors in Breast Cancer, 2002; International Agency for Research on Cancer, 2004)" (p. 11)

Both sources mention that a minority of studies have found a link between smoking and breast cancer in certain instances and that - as ever - more research is needed, but as the evidence stands, there is not a convincing link.

Any lay person reading your report cannot fail to conclude that obesity is the main driver of breast cancer, closely followed by drinking and smoking. This is untrue and should be corrected.

All the best,

Chris Snowdon

And, while we're at it, here's the unanswered e-mail I sent to the BBC last time Michelle Roberts misled women about breast cancer risks ('Passive smoking 'raises breast cancer risk'- 02.03.11)

Sir/Madam,

The story that appeared on the health section of your website today titled "Passive smoking 'raises breast cancer risk'" is inaccurate and misleading. Your use of quotation marks seeks to distance yourself from the claim that passive smoking raises breast cancer risk but the authors of the study you reference make no such claim either.

Even a cursory reading of the study reveals that the researchers say that "extensive exposure to passive smoking *may* increase breast cancer risk." They add that "the association with passive smoking should be considered suggestive only." Your headline does not reflect these doubts, nor does your report mention that the results found were statistically insignificant. You also focus on the highest relative risk (32%) when the overall relative risk was just 8%. You compound this by prefacing it with the words 'for example', thereby implying this was a typical finding rather than the most extreme scenario. Using the same study I could equally say that 'for example' women who are exposed to passive smoke in the home are 11% *less* likely to get breast cancer.

Finally, you claim that this study is the largest yet undertaken. This is untrue. Several studies have been larger including Peto et al (see below).

Before scaring and misleading your readers, you should make it clear that decades of research have shown that neither smoking nor passive smoking increases the risk of breast cancer. A 2002 review in the British Journal of Cancer, for example, looked at 53 studies and concluded that "smoking has little or no independent effect on the risk of developing breast cancer." An extensive review by Richard Peto in 2008 concluded: "incidence of breast cancer is similar in women who did and did not report passive exposure to tobacco smoke either as a child or as an adult."

There is no reason to report today's highly equivocal study as proof when you have not, to my knowledge, reported any of the dozens - possibly hundreds - of studies showing no effect.

Lax reporting of health stories seem to be endemic at the BBC of late. I appreciate the press releases you receive may sensationalise the findings in epidemiological studies, but it is time the BBC realised that medical journals are magazines like any other and rely on news coverage to maintain their profile, readership and advertising income. Press releases from these journals should be treated with the same caution as would press releases from any other business. If there is no one at the BBC who can (a) understand statistics and (b) make themselves familiar with the scientific literature, then you should either find someone who can or stop reporting these stories entirely.

Where do they find these bloody people?