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.
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.
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).
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.
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.