ASBrS: Time to pull the plug on thermography for breast screening?
Two factors spurred Cara Marie Guilfoyle, MD, breast fellow at Bryn Mawr Hospital in Bryn Mawr, Pa., and colleagues, to conduct the study: too many benign biopsies are likely performed based on suspicious imaging abnormalities and women are requesting an alternative to radiation-based imaging techniques.
No-Touch Breast Scan (NTBS), the infrared thermography system used in the study, is a noninvasive, non-radiation-based imaging tool. It employs dual infrared cameras and computer analysis to measure differences in blood flow. Angiogenesis typically increases blood supply, which shows up as temperature differentials after computer analysis, explained Guilfoyle during a May 4 webinar.
NTBS scans are scored on a scale of zero to 10, with 0 to 3 corresponding with slight temperature differentials and low-risk results. Scans rated between four and 10 are considered positive, with higher scores correlating with greater temperature differentials.
Guilfoyle and colleagues sought to determine if the system could predict breast cancer in patients undergoing minimally invasive biopsies for suspicious abnormalities.
The researchers enrolled 181 patients with 187 abnormalities between October 2009 and May 2011. All women underwent a thermography scan prior to biopsy and researchers compared pathology results obtained at biopsy with scan results. In addition, the normal opposite breasts of all study participants were screened using infrared thermography.
Guilfoyle et al initially used a higher specificity computerized analysis mode on the thermography system to minimize false positives. However, an interim analysis indicated that the sensitivity was too low with this approach, said Guilfoyle. The researchers then shifted to a higher sensitivity mode and also retroactively analyzed all data using the higher sensitivity mode.
The high specificity mode provided a sensitivity of 50 percent among the 52 women later diagnosed with breast cancer, and sensitivity was lower with early-stage ductal carcinoma in situ than with invasive disease. Among the 132 negative biopsies, 42 presented with positive infrared findings, resulting in 67 percent specificity.
When researchers analyzed data using the high sensitivity mode, infrared thermography delivered a sensitivity of 87 percent. However, 61 of the 116 negative biopsies were incorrectly identified as positive, and 22 patients were excluded due to uninterpretable thermography scans.
Thermography scans of the 173 normal contralateral breasts resulted in 24 percent positive results in the high specificity mode and 47 percent positive in the high sensitivity mode, Guilfoyle et al reported. To date, no cancers have been found in these breasts through routine radiologic screening.
“Certainly, these findings fail to point out a useful role for infrared thermography in our patient population. In the contralateral normal breasts, we were faced with 72 patients found positive on thermography but who showed no mammographic abnormalities,” Andrea V. Barrio, MD, breast surgeon at Bryn Mawr Hospital, said in a statement. “Therefore, our research shows infrared thermography cannot be used as a successful adjunct to mammography nor can it replace any of the screening modalities in standard practice today. Mammography remains the gold standard.”