By Monica J. Smith
Phoenix—Dashing hopes that infrared thermography could help distinguish malignant from benign lesions on imaging studies, research presented at the 2012 meeting of the American Society of Breast Surgeons suggests the noninvasive, radiation-free exam is not a useful tool for breast cancer screening.
“We recognize that we see a lot of false-positives with mammography and that we do a lot of unnecessary biopsies, but we need to detect all the cancers we do; we don’t want to miss any,” said lead investigator Andrea Barrio, MD, FACS, a breast surgeon at Bryn Mawr Hospital, in Philadelphia.
Infrared thermography is of great interest to patients attracted to the possibility of a noninvasive screening method that does not involve radiation. “We get questions weekly by patients who ask, ‘can I get this done instead?’” Dr. Barrio said. “Many centers use it adjunctively.”
Infrared thermography is based on the concept that a breast harboring cancer will be warmer than a normal breast due to the angiogenesis required to sustain a tumor.
NTBS [NoTouch BreastScan] thermography was unable to discriminate between benign and malignant lesions in women with suspicious imaging abnormalities in the low specificity mode.
Another issue is that NTBS does not pinpoint an area in the breast; it merely identifies that one breast is warmer.
If their study had found infrared thermography useful, Dr. Barrio and her colleagues saw a role for it not in place of, or as an adjunct to, mammography, but to avoid biopsy in situations where a patient had an imaging abnormality but a negative NoTouch BreastScan (UE LifeSciences; NTBS), using the name of the product in the study.
“We could say to them, ‘if your infrared is negative, then we can just watch these calcifications because we’ve never found a negative infrared in someone with cancer,’” Dr. Barrio said. “But it didn’t pan out that way.”
Since the 1982 FDA approval of an infrared device as an adjunctive tool for breast cancer screening, many such devices have been approved for that purpose. They are based on the concept that a breast harboring cancer will be warmer than a normal breast due to the angiogenesis required to sustain a tumor.
The subject of Dr. Barrio’s study, the NTBS uses dual infrared cameras and computer analysis to detect differences in blood flow that might show up as temperature differences, comparing breast surface thermal abnormalities and asymmetries.
The institutional review board–approved, nonrandomized trial consisted of 181 patients with 187 imaging abnormalities on mammography, ultrasound or magnetic resonance imaging, all of whom received an NTBS prior to minimally invasive biopsy. The researchers then compared tissue pathology with NTBS results.
The study was originally set to a higher specificity mode in an attempt to minimize false-positives, but when the researchers did a midterm analysis of the data in 2010, they recognized that the sensitivity was too low to detect cancers, so they shifted to a higher sensitivity mode.
Of the 178 patients evaluated in the prospective portion of the trial, 50 patients had 52 positive breast biopsies and 128 had 132 negative biopsies. In the higher specificity mode, NTBS was positive in only 26 patients. The normal contralateral breasts were scanned too, with a positive finding in 24%.
In the higher sensitivity mode, a retrospective evaluation, 22 more patients were excluded due to uninterpretable scans. Of the 156 remaining, 44 patients had 42 positive breast biopsies and 112 had 116 negative biopsies. Of the 46 positive biopsies, 40 had a positive NTBS, for a sensitivity of 87%.
“Unfortunately, this led to a dramatic decrease in specificity,” Dr. Barrio said, noting NTBS identified 47% of the contralateral breasts as positive this time.
“Our conclusion is that NTBS thermography was unable to discriminate between benign and malignant lesions in women with suspicious imaging abnormalities in the low specificity mode. When we went to the higher sensitivity mode, it still missed about 13% of the cancers and resulted in an unacceptable number of false-positives,” Dr. Barrio said.
Another issue is that NTBS does not pinpoint an area in the breast; it merely identifies that one breast is warmer. “It’s a functional scan, not a structural one, so it does have some problems. If you have one breast that’s hotter than the other, how far do you go in looking for an abnormality while being aware of the high number of false-positives that exist?” Dr. Barrio said.
The maker of the NTBS, who is from India and envisions his invention being used to identify women who should undergo further screening in places where mammography is rare, thought the 87% sensitivity was good, Dr. Barrio reported. “And it is, but that’s 87% as sensitive as a mammogram. It was concerning to us that it missed that percentage of cancers and that the false-positive rate was high.”
The findings were disappointing to Dr. Barrio’s team, and certainly to
“Out here in Los Angeles, and I’m sure in many other areas of the country, this is a hot topic among patients, especially given some of the studies raising concerns about radiation exposure from imaging tests,” said Deanna J. Attai, MD, Center for Breast Care, Inc., in Burbank, Calif.
“The promise of thermography is that it can give an idea of the activity of breast tissue without exposing the patient to radiation—amazing. Unfortunately, the results just do not hold up,” Dr. Attai said. “While we all recognize that mammography has limitations, especially in younger women and in women with dense breast tissue, at this point it is still the best overall screening test that we have.”
The sun has not completely set on infrared thermography, however. Dr. Barrio’s group also conducted NTBS on a number of women at high risk for breast cancer, those with a family history or atypia on a past biopsy, to see what happens down the road. At this point, these women do not have imaging abnormalities, but the researchers are investigating the possibility that even if infrared thermography fails to detect present tumors, it may be able to warn about future cancers.
“We hope to look over time to see, if they had an abnormal infrared, did [the infrared] predict anything for the future, and if they do develop a cancer in that time period, what did their infrared look like when we first screened them,” Dr. Barrio said. “I don’t know that we’ll have an answer to that anytime soon, but it will be something interesting to look out for.”