Breast cancer – Seeing red

It’s a truism that our greatest anxieties are also our most vulnerable points. Having kids is the best example but somewhere in many people’s top 10 will be a lurking concern over cancer. And, human nature being what it is, you can be sure that another lurking hazard is those who would exploit our weaknesses for commercial gain. A recent article in one of the most prestigious cancer journals has highlighted an example that deserves wider publicity. At issue are the relative merits of two methods for the detection of breast cancer – mammography and thermography.

Mammogram of a normal breast. American College Of Radiology

Mammography

Breast cancer screening is currently a topic of some debate in the light of reports that such programmes may be of little or no cost benefit. The standard method is mammography: this uses low energy X-rays to obtain images of tissue within the breast from which abnormalities may be identified. As the controversy reflects, it’s not perfect. There’s a threshold size below which tumours can’t be detected, there are false positives (abnormal mammograms not due to cancer), tumours that are difficult to spot (because of high tissue density), abnormal growths that get picked up but are not life-threatening – and the subject is exposed to ionizing radiation which itself can promote cancers.

Breast thermogram

Thermography

Perhaps more helpfully called thermal imaging, this method detects infrared radiation, which increases with temperature so that warmer things stand out from cooler. In effect you get a surface heat map – in animals of skin temperature, which rises as blood flow increases. As growing tumours stimulate the growth of new blood vessels, they can show up in thermograms.

What’s the difference?

Well, it’s sensitivity. A number of studies have concluded that, although thermography is non-invasive and painless, it’s just not sensitive enough to be used as a routine screening test for breast cancer. The US Food and Drug administration (FDA) – responsible for protecting and promoting public health – has this to say: ‘…thermography is not a replacement for screening mammography and should not be used by itself to diagnose breast cancer. The FDA is not aware of any valid scientific data to show that thermographic devices, when used on their own, are an effective screening tool for any medical condition including the early detection of breast cancer or other breast disease’.

Why the fuss?

What upset the authors of the article is that direct-to-consumer advertising is presenting thermography as an effective breast cancer screening method on the basis of misleading information and that this may be damaging if it persuades women to forsake mammography, imperfect though that may be. ‘Misleading’ includes exaggerating the sensitivity of thermography, suggesting that having a mammogram could promote tumour spread (for which there is no evidence that I know of) and the claim that thermography is ‘FDA approved’ (no, you didn’t misread the last paragraph).

Bottom line

There’s a place for everything – except for deliberate misrepresentation: cancer’s too difficult and too important for that. And the gold standard for monitoring breast cancer remains the ‘triple test’: physical breast examination, imaging (mammogram, possibly supplemented with ultrasound and/or magnetic resonance imaging) and removal of cells for pathological examination.

References

Lovett, K.M. and Liang, B.A. (2011). Risks of online advertisement of direct-to-consumer thermography for breast cancer screening. Nature Reviews Cancer 11, 827-828.

Raftery, J. and Chorozoglou, M. (2011). Possible net harms of breast cancer screening: updated modelling of Forrest report. British Medical Journal 2011;343:d7627 

Food and Drug Administration (2011). FDA Safety Communication: Breast Cancer Screening – Thermography is Not an Alternative to Mammography [online]

Kontos, M., Wilson, R. & Fentiman, I. (2011). Digital infrared thermal imaging (DITI) of breast of breast lesions: sensitivity and specificity of detection of primary breast cancers. Clin. Radiol. 66, 536–539. 

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Third-hand smoke

Most people who read this will know that the major cancer world-wide is lung cancer (both new cases and deaths), most of which (about 90%) are due to tobacco use. Anti-smoking publicity has been effective in parts of the developed world, and it’s drawn attention to the risks of ‘second-hand’ or ‘passive’ smoking – known since the 1930s – with the result that, at last, smoking is now banned in many public places.  This has contributed to the decline in the number of men dying from lung cancer in both the USA and the UK since 1980. It’s also helped to stabilise over the last 10 years the lung cancer death rate of American women although, as ever, the Brits are lagging behind and the rate for British women is still rising.

An additional facet of this problem has recently begun to be recognized in the form of ‘third-hand smoke’ – meaning that residual contamination may be present long after someone has smoked in the area. Inevitably, Sod’s Law appears to apply in that the chemicals that hang around by sticking to surfaces include some of the more toxic of the 1000 or so in cigarette smoke. No non-smoker who has tried snuggling up to a smoker or merely been ushered into a hotel room previously occupied by one will need convincing of the reality of  ‘third-hand smoke’. However, a recent study from the University of Rochester Medical Center in New York has thrown an alarming light on the combined effects of second- and third-hand smoking by showing that children living in apartments suffered substantially greater exposure to tobacco smoke compared with those living in detached homes, even when no one smoked in their household. The conclusion came from measurement of the blood levels of a substance called cotinine, which is produced from nicotine and gives a quantitative estimate of exposure to tobacco smoke.

No study of this type is without its weaknesses – an obvious one in this case being that you can only go on what you are told about whether people smoke in their own homes. However, 5,002 children were studied, which is a reasonable number from which to make preliminary deductions, and the finding that those living in apartments had a 45% increase in cotinine over those living in detached houses is an arresting result.

It is clear that in explaining these results the distinction between ‘second’ and ‘third’-hand smoke becomes blurred but one factor would appear to be tobacco smoke disseminating through multi-unit apartments. Regardless of precise mechanisms, the authors leave us with the fact that most children in the US are exposed to tobacco smoke, including a proportion of those whose parents don’t smoke, despite the fact that we know the damage it can do. Recall that it is associated not only with the long-term risk of lung cancer but with a variety of illnesses of increasing incidence, particularly asthma, and that there is no such thing as a ‘safe level’ of exposure.

Reference

Wilson, K.M., Klein, J.D., Blumkin, A.K., Gottlieb, M. and Winickoff, J.P. (2011). Tobacco-Smoke Exposure in Children Who Live in Multiunit Housing. Pediatrics 127, 85-92.

http://www.quit-smoking-central.com/third-hand-smoke.html