Position Statements
The Use of thermography as a breast cancer screening or diagnostic tool
January 2005
Position
The National Screening Unit (NSU), the Cancer
Society of New Zealand and The New Zealand
Breast Cancer Foundation do not support the use
of thermography as a breast cancer screening or
diagnostic tool as there is insufficient evidence
to do so.
Thermography
Clinical thermography is the recording of
heat distribution in order to form an image
(a thermogram) of the temperature distribution
on the surface of the body. Thermography has
been used in medicine since the 1960s and has
been promoted as a tool in the early detection
of breast cancer. Whilst not well understood,
the underlying mechanisms for the raised temperature of a breast cancer include increased
tumour metabolism and elevated blood flow. (ref. note 1)
The detection of cancer is based on differences
in temperature distribution compared with the
other breast. Thermography has been promoted
as particularly useful in the detection of
abnormalities in women aged 30–50 years,
women with small breasts and women with
breast implants.
History of thermography
Thermography was used and studied in the 1960s
and 1970s, with up to 3,000 thermography clinics
operating in the US at this time.(ref. note 1) Two important
trials in this period involved thermography.(ref. note 1)
The first(ref. note 2) compared the use of thermography, an
early form of mammography (xeromammography)
and clinical examination as a screening tool
in a clinical trial involving 16,000 women.
Thermography’s sensitivity and specificity
were 39% and 82% respectively, compared with
xeromammography’s 78% sensitivity and 98%
specificity. In a separate trial, the Breast Cancer
Detection Demonstration Project (BCDDP)
planned to compare thermography, mammography
and clinical examination, but dropped
thermography early in the project due to a high
false positive rate and low sensitivity.(ref. note 3)
Following
these trials, thermography was largely abandoned,
but technological advances in recent years have led
to renewed interest in the technology.(ref. note 1)
Thermography in New Zealand
Thermography is currently being marketed to
women and general practitioners in New
Zealand. The National Screening Unit, the
Cancer Society of New Zealand and The New
Zealand Breast Cancer Foundation have been
concerned about the use of thermography as
a tool in the screening and diagnosis of breast
cancer, since women who undergo thermography
may delay visiting their doctor with a significant
symptom, or attending for screening
mammography, if they believe that thermography
is an adequate replacement for a doctor visit
or a mammogram.
Thermography has been promoted in New Zealand
as both a breast screening and diagnostic tool.
Screening and diagnostic tools serve different
functions and adhere to different standards.
Screening
Women are invited to participate in screening
on the understanding that, overall, participating
in screening will, when all the risks and benefits
are considered, be beneficial to them. This is in
line with international minimum standards for
screening. It is vital that any new screening test
is assessed through well-conducted medical
research – ideally randomised controlled trials
(RCTs) or meta-analyses of RCTs.(ref notes 4-6)
Diagnosis
The role of a diagnostic test is to evaluate
abnormalities that have been detected either
clinically or by screening. To be clinically
efficacious, a diagnostic test must allow a
confident characterisation of the nature of a
lesion and be shown to alter patient management
for the better.(ref note 7)
Systematic Review
In December 2003 the National Screening Unit
commissioned a systematic review of the
international literature on the effectiveness of
thermography for population screening and
diagnostic testing of breast cancer. This review
was conducted by the New Zealand Technology
Assessment Clearing House for Health Outcomes
and Health Technology Assessment (NZHTA)– a highly respected and impartial unit of the
University of Otago – using a rigorous methodology.
The review was completed in July 2004.
NZHTA reviewed studies evaluating the use
of infrared thermography as an adjunctive or
stand-alone tool for the population screening
of breast cancer and the role of infrared
thermography as an adjunctive tool for the
diagnosis of breast cancer.
The review established that there were no studies
that evaluated the effectiveness of the infrared
technology devices that are currently available in
New Zealand. In addition, there were few studies
that evaluated comparable infrared technologies
or technologies that may become available to
New Zealand. This was despite using a systematic
approach, which included a comprehensive
search strategy that identified 1,154 abstracts.
The review found that much of the recent
literature on infrared thermography is in the form
of narrative review, discussion or opinion
articles. Most of the published study reports on
infrared thermography refer to studies of infrared devices that are outdated or no longer available,
or non-infrared methods of thermography.
No studies of this technology have been
conducted in New Zealand.
NZHTA concluded that the evidence that is
currently available does not provide enough
support for the role of infrared thermography
for either population screening or adjuvant
diagnostic testing of breast cancer.
The NZHTA conclusions are consistent with
recommendations of key professional groups.
The Royal Australian and New Zealand College
of Radiologists Breast Imaging Reference Group
does not recommend the use of thermography for
the early detection of breast cancer.(ref note 8) Similarly,
the American Medical Association states that the
use of thermography for diagnostic purposes
cannot be recommended.(ref note 9) Thermography is not
used in either the United Kingdom or Australian
breast cancer screening programmes. The
International Agency for Research on Cancer
states that “…the sensitivity and specificity
of thermography are poor, and its application
to screening is unlikely.”(ref note 6)
Conclusion
The National Screening Unit, the Cancer Society
of New Zealand and The New Zealand Breast
Cancer Foundation do not support the use of
thermography as a breast cancer screening tool
or breast cancer diagnostic tool, as there is
insufficient evidence to do so.
If any health providers are offering thermography
to women, it is vital that women are fully
informed of the potential harms of thermography,
including the likelihood of false positive results
and false negative results, and typical annual
costs. This information should include an acknowledgement of the lack of proof of efficacy
and effectiveness of thermography as a screening
and diagnostic tool.
References
1. Nass SJ, Henderson C, Lashof JC. Mammography and beyond: developing technologies for the early detection of breast cancer: Institute of Medicine
and Commission on Life Sciences, National Research Council, 2001.
2. Feig SA, Shaber GS, Schwartz GF, Patchefsky A, Libshitz HI, Edeiken J, et al. Thermography, mammography, and clinical examination in breast
cancer screening. Radiology 1977;122(1):23-127.
3. Moskowitz M. Thermography as a risk indicator of breast cancer. Results of a study and a review of the recent literature. Journal of Reproductive
Medicine 1985;30(6)):451-459.
4. National Health Committee. Screening to improve health in New Zealand: Criteria to assess screening programmes. Wellington: National Health
Committee, 2003.
5. Muir Gray JA. Evidence-based Healthcare. 1st ed. Edinburgh: Churchill Livingstone, 1997.
6. International Agency for Research on Cancer (IARC). Breast Cancer Screening. 1st ed. Lyon, France: IARC Press, 2002.
7. Orel SG, Troupin RH. Nonmammographic imaging of the breast: Current issues and future prospects. Seminars in Roentgenology 1993;28:231-241.
8. Royal Australian and New Zealand College of Radiologists Breast Imaging Reference Group policy on the use of thermography to detect breast
cancer 2001. http://www.ranzcr.edu.au/open/policies/diagnostic_imaging/pol7_3.htm
9. American Medical Association thermography update H-175.988: AMA Policy Finder undated.
http://www.ama-assn.org/apps/pf_new/pf_online?f_n=browse&doc=policyfiles/HnE/H-175.988.HTM
