In order to understand the hopes placed on this test, one needs to understand the underlying physiologic mechanisms of the procedure. The mechanism is purely neurovascular and involves a primitive survival reflex initiated from peripheral neural receptors and conveyed to the central nervous system. To protect the body from hypothermia, the reflex invokes a sympathetically mediated blood vessel constriction in the periphery in an attempt to maintain the normal core temperature set point.
Blood vessels produced by cancerous tumors are simple endothelial tubes devoid of a muscular layer and the neural regulation afforded to embryologic vessels. As such, these new vessels would fail to constrict in response to a sympathetic stimulus. In the normal breast, test results would produce an image of relative cooling with attenuation of vascular diameter. A breast harboring a malignancy would theoretically remain unchanged in temperature or demonstrate hyperthermia with vascular dilation.
However, to date it has not been found that the stress test offers any advantage over the baseline images. For well over a decade, leading experts and researchers in the field of infrared breast imaging have discontinued the use of the cold challenge. Yet, in a 2004 detailed review of the literature combined with an investigational study, the validity of the cold challenge test was explored. Results from 23 patients with histologically confirmed breast cancers along with 500 non-cancer cases were presented demonstrating positive and negative responses to the challenge. From the combined literature review and study analysis it was found that the test did not alter the clinical decision-making process for following up suspicious thermograms, nor did it enhance the detection of occult cancers found in normal thermograms.
In summary, it was found that there was no evidence to support the use of the cold challenge. The study noted insufficient evidence to warrant its use as a mandated test with all women undergoing infrared breast imaging. It also warned that it would be incorrect to consider a breast thermogram “substandard” if a cold challenge was not included. In conclusion, Dr. William C. Amalu who conducted the review stated: “Until further studies are performed and ample evidence can be presented to the contrary, a review of the available data indicates that infrared imaging of the breast can be performed excluding the cold challenge without any known loss of sensitivity or specificity in the detection of breast cancers.”
We have advanced significantly in our understanding of physiology and how thermography can be effectively used. No technology stands still, we expect science to advance, medical knowledge to improve and evolve and we have to be prepared to learn from experience….. both our own and others. I have no doubt that there will be ongoing advances in thermographic imaging and they may even include new forms of stress testing but the best way to move forward is to learn from experience and then look ahead rather than back.