Introduction: Nonlinear microscopy (NLM) is a novel technology that can quickly image fresh surgical specimens at adjustable depths and produce digital images resembling standard hematoxylin and eosin (H&E) histology. We have previously demonstrated the ability to accurately differentiate prostate cancer from benign glands using NLM (Cahill et al 2020). Intraoperative margin evaluation using frozen section during radical prostatectomy (RP) has been shown to improve nerve-sparing (NS) rates and decrease positive surgical margins (Schlomm et al 2012) but is time and resource-intensive and has not been widely adopted. We describe a new method to evaluate RP margins using NLM, present preliminary data on feasibility and compare NLM with paraffin embedded H&E staining.
Methods: NS-RP or non NS-RP was performed per standard of care. The neurovascular bundle, if present on the prostate, was dissected off ex vivo to simulate nerve-sparing and this margin inked separately. The specimen was inked and grossed into standard whole mount slices. Pathology staff were previously trained in NLM slide preparation and cancer identification. Margins were evaluated using NLM, and the tissue subsequently processed for standard paraffin embedded H&E (see Figure 1). After an initial trial period of 3 patients, the timing of the NLM process was recorded to assess intraoperative feasibility.
Results: 23 participants were included in the analysis. NLM evaluation correctly identified 7 cases with positive margins and 10 with negative margins. In 5 cases, tumors closely approached the margin and were cautiously deemed equivocal by NLM. All of these cases were ultimately negative on paraffin-embedded H&E. 1 case was falsely negative by NLM, but focally positive on H&E. The average time for NLM processing (inking, grossing, and evaluation) was 36 minutes. Transportation from the operating room to the NLM unit required an additional 6 minutes.
Conclusions: This study suggests the feasibility of RP margin evaluation using NLM without compromising final H&E margin status. A clinical workflow has been developed for prospective evaluation of prostate margins during RP using NLM.