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Why thermography may not be so hot
 SOME wonder if thermography should be considered for breast cancer screening programmes in Singapore. This involves using infrared cameras to take colour-coded digitised pictures of the varying temperatures of the surface of a human body. The idea here probably came from a recent episode of Oprah that had a doctor making a pitch for this 35-year-old technology. Note, however, that the doctor in question also suggested that women learn to direct qi (or life force, according to Chinese cosmology) into the vagina. On another episode of Oprah, Dr Christiane Northrup had demonstrated just how to do this.
Apparently, using various breathing exercises, this practice can cure all sorts of feminine ills – and spice up a woman’s sex life to boot. These days, however, Dr Northrup has taken to pushing thermography, a technology that has much more plausible theoretic underpinnings than qi directed into vaginas. In cancerous tumours, cells grow very rapidly and their rate of metabolism is very high. In cancers, several new blood vessels also develop to bring more blood, and thus more oxygen and more nutrients, that they need to sustain their uncontrolled growth. As such, a cancer should be warmer than the healthy tissues around it.
The human body emits infrared radiation which can be caught on special cameras. When healthy, different parts of the body have different thermal patterns. Thus each breast’s thermal pattern is like a fingerprint – if taken in exactly the same position each time – that does not change over time. However, if breast cancer develops, the skin temperature over the breasts may be raised by 2 or 3 deg C. Therefore, if a woman had a normal baseline breast thermogram done earlier, any significant change in the thermal pattern later on could indicate some cancerous growth.
Thermogram vs X-ray mammogram
In effect, a thermogram offers a functional picture of the biological activity inside a tumour – that is, of increased blood vessel growth and hyperactive cell metabolism. By contrast, a conventional X-ray mammogram offers a purely structural picture of a lump (or, actually, its shadow). Advocates like Dr Northrup love to highlight just
how the technology was approved by the United States Food and Drug Administration (FDA) for the detection of breast cancer. What they leave unsaid, though, is that it was approved for this purpose only when used in conjunction with conventional mammography.
Moreover, it is also always left unsaid that thermography fell out of favour because a large study of 16,000 women in 1977 showed it to be a poor screening tool. While mammography picked up 78 per cent of all breast cancer cases, thermography picked up only 18 per cent of them. Of course, technology has improved since. Digital technology means that thermal sensors can detect temperature differences as small as 0.08 deg C. In addition, advanced computer software analysis of the thermal patterns means that reading them is no longer as subject to human error as it used to be. In the past, a lack of people trained to analyse the images was a serious drawback to using thermography.
But whether the technology has advanced so much that thermography may serve as an efficient screening tool for breast cancer remains unestablished. This is because there has not been even a single rigorous clinical trial that has been done to ascertain how sensitive and specific the technology might be. (The former refers to how efficiently it picks up breast cancers that are really there; the latter refers to how often the tumours it reports are really cancers and not just artefacts.)
Lack of scientific evidence
In addition, economic studies will be needed to ascertain if it is a cost-effective method to be used in public
screening programmes. This is because whatever information thermography can provide, the functional MRI scan can provide even better (as it can show actual blood flow in real time). Moreover, functional MRI can
also be used to guide the surgeon’s biopsy needle whereas thermography cannot do this.
The economics will matter if thermography is to be chosen over the costly MRI for screening, both of which do not involve X-rays that may harm women, a fear some have with mammograms. For all these reasons, no health authority has deployed thermography for public screening. Indeed, in February, the US National Breast and Ovarian Cancer Centre announced it “does not recommend the use of thermography for the early detection of breast cancer... There is no current scientific evidence to support (it)”. The statement also noted that this position was “in agreement with BreastScreen Australia and the Royal Australian and New Zealand College of Radiologists’ statements on use of thermography to detect breast cancer”.
Many factors other than cancer can affect the temperature of the skin over the breasts. These include the woman having imbibed alcohol or coffee or smoked, exerted herself physically, powdered her chest heavily, massaged the breasts, being on female hormones, being pregnant or menstruating, and so on. Until its use is standardised and the technology proven to be sensitive and specific in picking up breast cancers, thermography should be regarded as experimental. It should be offered only within a clinical trial.
The technology itself is not the province of quacks. Pushing it as a sure and better method for breast screening, however, is quackery. Beware of those who do so out of pecuniary interests.
Q & A on thermography
Q: “Could thermography be a better alternative?”
MS AUDREY CHEONG: "Although mammograms do serve a purpose, there have also been cases of breast cancer being detected between mammogram screenings. Could thermography be a better alternative, although it may be more costly? There seems to be an absence of local references to this form of screening."
A: “Screening mammography is still recognised as the gold standard.”
DR SHYAMALA THILAGARATNAM, Director, Healthy Ageing Division, Health Promotion Board; DR JILL WONG, Senior Consultant Radiologist, National Cancer Centre Singapore, Chairperson of Breast Screen Singapore Quality Assurance and Training Committee: “We refer to Ms Audrey Cheong’s letter: Thermography or thermal imaging uses infrared rays to measure the temperature of the skin of the breast. The rationale is that the temperature of the area around a developing breast cancer is higher than that of normal breast tissue.
Currently, there is insufficient scientific evidence to support thermography’s efficacy as a routine screening test for detecting breast cancer early. Screening mammography is still recognised as the gold standard for breast cancer screening as it is proven to be able to detect cancers in the initial stages, when there are usually no
symptoms or signs. In fact, mammography is the only screening test approved by the United States Food and Drug Administration for detecting breast cancer.”
Ref: V10
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