OCT allows better planning of Mohs surgery
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CHICAGO — OCT accurately staged skin cancers, allowing for better diagnosis of basal cell carcinoma, prediction of margins and improved planning for Mohs surgery, according to a study presented here.
“Mohs surgery is considered the gold standard for treating high-risk basal cell, yet as we all know, it’s not a perfect system. For one thing, it’s expensive. For another, it’s time consuming,” Sruti S. Akella, MD, of the University of Illinois Eye and Ear Infirmary, Chicago, said at the ASOPRS Fall Scientific Symposium. “Finally, it can be unpredictable. What I mean by that is there’s no way to anticipate tumor margins before Mohs. The reconstructive surgeon and patient may encounter unpleasant surprises like these in which the actual defect turns out to be much larger than the anticipated defect. We do need a way to predict tumor margins before surgery. It turns out that one way we could do this is with cutaneous OCT.”
The study included patients older than 18 years with treatment-naive, biopsy-proven basal cell carcinoma (BCC) who were referred for Mohs microsurgery. Patients with recurrent BCC or BCC arising in a previous surgical site were excluded. Twenty-two patients were enrolled between October 2021 and March 2022.
Akella showed the handheld probe used for cutaneous OCT and explained that it was applied to the lesion at cardinal time points. The images were sent to a masked panel of non-dermatologists who analyzed the images for clinical features and made a prediction whether there was tumor extension that would require a second stage of excision.
“What we found was actually quite striking. Even though all 22 patients were confirmed to have BCC based on their initial biopsy, by the time these patients reached the Mohs surgeon weeks later, histopathology proved that only 15 of them had true residual BCC,” Akella said. “It turns out that in these instances, OCT could not detect any evidence of malignancy at any location. But neither could histopathology. It seems very likely that these smaller lesions are actually regressing spontaneously in the weeks following biopsy, and when we perform Mohs, we are vastly overtreating these patients.”
OCT predicted a lack of tumor in six out of seven cases (86%) with one false positive.
After confirming true BCC, 15 patients underwent Mohs surgery. Nine underwent a single-stage procedure, and six underwent a two-stage procedure.
OCT correctly predicted the single-stage outcome in seven of the nine cases (78%) and in all nodular subtypes. The prediction was accurate in five of the six two-stage excisions (83%).
“This is a really exciting application of cutaneous OCT, and with further research and understanding of the technology’s limitations, it really does have the potential to fundamentally alter how we treat and approach skin cancer,” Akella said.
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Akella SS, et al. Measure twice, cut once. Presented at: ASOPRS Fall Scientific Symposium; Sept. 29-30, 2022; Chicago.
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