SAN DIEGO – In assessing tumor-free margins during Mohs micrographic surgery for skin cancer, of histologic sections, in a single-center, pilot study of bioimpedance in 151 specimens from 50 consecutive patients.
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If the finding of high diagnostic accuracy using bioimpedance spectroscopy is confirmed in larger numbers of patients and specimens run at multiple sites, this approach could “potentially revolutionize what happens with the way Mohs sections are processed in the future” by potentially shaving many minutes off the duration of a standard procedure, Darrell S. Rigel, MD, said in a video interview during the annual meeting of the American Academy of Dermatology.
Usually, it takes 10-20 minutes to process and examine Mohs specimens at each stage of the surgical procedure to determine whether additional excision must remove residual cancer cells, said Dr. Rigel, a dermatologist at New York University. In contrast, assessment for residual cancer cells in the surgical field takes less than a minute using bioimpedance spectroscopy, which relies on differences in electrical conductivity between benign and cancerous cells to identify cancer cells remaining at the surgical margins.
The results of the study were presented in a poster at the meeting, by a research associate of Dr. Rigel’s, Ryan Svoboda, MD, of the National Society for Cutaneous Medicine, New York.
The researchers used a bioimpedance spectroscopy device made by NovaScan to assess 151 histology slides prepared during Mohs micrographic surgery on patients with nonmelanoma skin cancer, and compared the findings against the gold standard of histological slide examination. By this criterion, bioimpedance spectroscopy identified 105 true negatives and 2 false negatives, and 43 true positives and 1 false positive. Calculations showed that this equated to 95.6% sensitivity, 99.1% specificity, a 97.7% positive predictive value, and a 98.1% negative predictive value.
These may be underestimates of the accuracy of bioimpedance spectroscopy because the calculations presume that conventional histology is always correct, but Dr. Rigel noted that sometimes the histological diagnosis is wrong.
SOURCE: Svoboda R et al. Poster 7304.