OCT tumor visualization ‘disappointing’
MedWire News: Optical coherence tomography (OCT) successfully identifies basal cell carcinoma (BCC) ex vivo during Mohs micrographic surgery, research shows.
However, tumor visualization with OCT was "disappointing," report Daniela Cunha (St John's Institute of Dermatology, London, UK) and colleagues in the British Journal of Dermatology.
The researchers suggest that OCT might be optimized if combined with other diagnostic tools.
Mohs micrographic surgery has a high cure rate for nonmelanoma skin cancers, explain the authors. The surgery spares normal tissue, but is time-consuming compared with traditional surgery because the margins of the tumor are excised layer by layer until the tumor is removed.
The purpose of the present study was to compare the efficiency and accuracy of ex vivo OCT with frozen-section histology for identifying BCC in Mohs surgery.
For each of the patients enrolled in the study (n=38), images of BCC were captured using an OCT microscope after the first and/or second stages of tissue were removed and processed for standard histology.
The OCT images were compared with the haematoxylin-eosin sections at approximately the same depth from the superficial margin. In total, 75 sections were scanned with the OCT microscope.
Cunha et al report that the mean time to produce one OCT image was 7 minutes, compared with 40 minutes to produce one haematoxylin-eosin section.
Overall, there was poor concordance between OCT images and the frozen-histology sections. Specifically, just four of the 26 BCC-positive specimens, and 23 of the 49 BCC-negative specimens showed good correlation between OCT images and the haematoxylin-eosin sections when assessed by two surgeons.
In the remaining 48 specimen sections, the images were either too vague to make a diagnosis or incomplete sections were obtained.
The sensitivity of OCT in the diagnosis of BCC in the present series was 19%, the specificity was 56%, and the positive predictive value was 18.2%. These findings contrast sharply with other reports showing sensitivity ranging from 79% to 94% and specificity ranging from 85% to 96% in differentiating normal skin from general skin lesions in vivo, remark Cunha and colleagues.
They note that there might be reduced contrast with OCT images obtained ex vivo, "possibly as a result of increased optical scatter in unperfused tissue."
Overall, OCT - as used in this study - needs to be "optimized in order to achieve acceptable levels of evidence and a practical benefit," concludes the team.
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