The Clinical Therapeutics Committee (CTC) does not recommend use of screening breast thermography in naturopathic practice. We are concerned about uncertain benefits in the face of substantial harm.
Digital infrared thermal imaging (DITI) of the breast (or breast thermography) is recommended by some naturopathic doctors for the purpose of screening for tumour neovascularity as an early sign of breast cancer. It is often advocated in the context of proactive breast health.
In November of 2012, Health Canada provided an information update advising Canadians and health care practitioners that thermography devices have not been approved to screen for breast cancer in Canada.1 The Health Products and Food Branch Inspectorate, Health Canada, forwarded a direct communication to the Canadian Association of Naturopathic Doctors (CAND) reiterating their concerns. An ensuing discussion occurred among naturopathic stakeholders including the Board of Directors of Drugless Therapy - Naturopathy, CAND, Naturopathic Doctors Ontario, and the CCNM CTC*. This article summarizes the CTC’s position on the clinical use of screening breast thermography.
The evidence base in support of modern era thermography as a standalone or adjunctive test for breast cancer screening is limited to a few small studies.2,3 For a recent review of the evidence we direct the reader to the open access 2012 article by Walker et al.3
Despite purported enhancements in modern DITI, the diagnostic accuracy of the method evaluated against histologically confirmed malignancy has varied substantially across studies.3 For instance, across two small studies, each examining patients on the basis of a high level of cancer suspicion, sensitivity was 25% in one study4 and 97% in the other.5 Specificity, parameters were reported as 85% and 44%, respectively. Kontos et al reported a positive predictive value of just 24% indicating that given a positive thermogram, the probability of a true malignancy was 24%.4,6
To the best of our knowledge, no large study has evaluated DITI performance against robust outcomes such as death from cancer or total mortality. Consequently, there are no data upon which to conduct a reasonable risk-benefit analysis of thermography screening for early stage cancer detection. By necessity -and intent- some positive thermography results will escalate cancer assessment and this will lead to known harms7 associated with standard screening. Harms include false-positive findings leading to psychological distress, biopsy pain, and economic costs of increased assessment. The most significant concern of the CTC is that of overdiagnosis (and thus aggressive treatment) of lesions that would never lead to clinically significant disease. The natural course of a ductal carcinoma in situ (DCIS) lesion is highly variable. If left untreated, up to 50% of cases progress to invasive disease.8 Conversely, greater than one half of lesions remain asymptomatic over the course of a woman’s lifetime. Early detection by screening mammography has not been shown to reduce DCIS associated mortality.9 Yet, DCIS detection contributes substantially to the burden of screening associated overdiagnosis.9 The CTC is concerned that routine thermography screening–even in the context of a functional breast assessment–will escalate the detection of non-invasive cancer and thus increase the rate of incident harm associated with the current Canadian standard of care.
Conventional Breast Cancer Screening
The CTC believes that mammography data are instructive for contextualizing harms associated with screening breast thermography. In Table 1 we present Canadian Task Force on Preventative Health Care data specific to average risk women between 40 and 49 years of age (patient risk-benefit summary sheets are available at: www.candiantaskforce.ca
). We provide data specific to the less than 50 years age group as it is this group where the overall benefit of breast screening is particularly uncertain (and thus not recommended by the Task Force), and women in this group, and younger, are a prime demographic target for advocates of proactive thermography screening.
Table 1. For women between 40 and 49 years of age receiving regular mammography screening:
1 in 3
… women will have a false positive mammogram requiring further screening.
1 in 28
… women will require a biopsy
1 in 200
… women will have part or all of a breast removed unnecessarily
2100 women would need to be screened every two years for 11 years to prevent one breast cancer death.Excerpted from Risks vs. Benefits Poster: For ages 40-49. Canadian Task Force on Preventative Health Care 10
While The Task Force guidelines continue to recommend mammography screening for average risk women aged 50 to 74 years11 some groups, such as the Nordic Cochrane Group (see: www.cochrane.dk
), propose that breast cancer screening, regardless of age, may produce no net benefit in overall cancer deaths and total mortality.12,13 The utility of DITI in this context remains unproven. Yet it is reasonable to assume that intensification of the screening process using DITI will involve harms, including increased anxiety, biopsy, and an overdiagnosis of cancers that would not have required treatment. In some women this will lead to unnecessary treatment including radiation, chemotherapy, and surgical removal of the breast each with their own constellation of morbidity and side effects.
The CTC Position
The CTC unanimously supports patient choice in the determination of health care needs. However, we believe that the choice must be truly informed, based on accurate, honest, and effectively contextualized information; this requires that providers present data that reasonably reflects potential harms, lack of benefit, and honest uncertainty. We endorse further study into potential benefits of adjunctive DITI, but only in the context of appropriately designed clinical studies. At this time existing evidence reveals no net value in DITI breast screening for the purpose of promoting proactive breast health. Moreover, we are concerned about uncertain benefits in the face of substantial harm.
1. Health Canada. Health Products and Food Branch Inspectorate. Thermography machines not authorized to screen for breast cancer. Information Update 2012-178. Available at http://www.hc-sc.gc.ca/ahc-asc/media/advisories-avis/_2012/2012_178-eng.php
[Accessed 5 Feb 2013].
2. Kennedy DA, Lee T, Seely D. A comparative review of thermography as a breast cancer screening technique. Integr Cancer Ther 2009 Mar;8(1):9-16.
3. Walker D, Kaczor T. Breast Thermography: History, Theory, and Use. Natural Medicine Journal. [Internet] 3-July-2012 [Accessed 5 Feb 2013] Available at: http://www.naturalmedicinejournal.com/article_content.asp?article=340
4. Kontos M, Wilson R, Fentiman I. Digital infrared thermal imaging (DITI) of breast lesions: sensitivity and specificity of detection of primary breast cancers. Clin Radiol. 2011;66(6):536-539.
5. Arora N, Martins D, Ruggerio D, Tousimis E, Swistel AJ, Osborne MP, Simmons RM. Effectiveness of a noninvasive digital infrared thermal imaging system in the detection of breast cancer. Am J Surg 2008; 196(4):523-6.
6. Neubauer K. Are breast thermograms accurate enough to use? Natural Medicine Journal [Internet] 2011. 01 Nov 2011 [Accessed 5 Feb 2013] Available at: http://www.naturalmedicinejournal.com/article_content.asp?edition=1§...
7. Jørgensen KJ, Keen JD, Gøtzsche PC. Is mammographic screening justifiable considering its substantial overdiagnosis rate and minor effect on mortality? Radiology 2011 Sept;260, 621-627.
8. Jones JL. Overdiagnosis and overtreatment of breast cancer: Progression of ductal carcinoma in situ: the pathological perspective. Breast Cancer Res. 2006; 8(2):204.
9. Kerlikowske K. Epidemiology of ductal carcinoma in situ. J Natl Cancer Inst Monogr 2010 (41):139-141.
10.Canadian Task Force on Preventative Health Care. Risks vs. Benefits Poster: For ages 40-49. [Accessed 5 Feb 2013] Available at http://canadiantaskforce.ca/guidelines/2011-breast-cancer
11.The Canadian Task Force on Preventive Health Care. Recommendations on screening for breast cancer in average-risk women aged 40–74 years. CAMJ 22 Nov 2011; 183(17):1991-2001.
12.The Nordic Cochrane Centre. Screening for breast cancer with mammography. Available at http://www.cochrane.dk/screening/index-en.htm
[Accessed 5 Feb 2013]
13.Gøtzsche PC, Nielsen M. Screening for breast cancer with mammography. Cochrane Database Syst Rev. 2011 Jan 19;(1):CD001877.