Objective: Surgical resection remains the gold standard for many solid tumors. Despite many novel techniques, positive margins are found in 15-30% of all head and neck cancer resections. Emphasizing the need to improve these outcomes, one approach to differentiate tumor-positive from tumor-negative margins could be real-time margin evaluation. Using the near-infrared fluorescently labeled anti-epidermal growth factor receptor (EGFR) antibody panitumumab-IRDye800, we previously showed that EGFR positive squamous cell carcinoma could be targeted with high sensitivity and specificity. The current study evaluates the use of panitumumab-IRDye800-based 3D fluorescence primary tumor surface mapping for margin assessment.
Materials and Methods: A first-in-human pilot study was performed in patients (n=8) after infusion of fluorescently labeled antibody, panitumumab-IRDye800 to allow surgical mapping of the tumor specimen. Patients underwent standard of care surgical resection for head and neck squamous cell carcinoma (HNSCC). Following resection of the primary tumor, the specimen was imaged using a novel closed-field imaging system optimized for IRDye800 (774 and 789 nm for excitation and emission, respectively; Li-COR Biosciences, Lincoln, NE, USA). This device creates a 3D volume rendering of the surgical specimen that offers the viewer (i.e. surgeon and/or pathologist) vital information regarding the locations of the tumor within the resected tissue and the distribution of the panitumumab-IRdye800-based fluorescence signal there. Then the specimen was sent for formalin-fixation and bread loafing. Thereafter, a hematoxylin and eosin slide was obtained from each bread loaf on which a board-certified pathologist outlined the tumor. Subsequently, we measured the tumor-edge to specimen-edge distances. To assess the fluorescence signal for each measured distance, we traced the slides back to the corresponding region in the original surgical specimen. Quantification of the fluorescence signal was done using a customized device integrated software program. To determine the predictive value of the device for margin assessment the fluorescence intensity was correlated with tumor distance.
Results: Optical mapping of the specimen had a 95% sensitivity and 89% specificity to detect cancer within 5mm (n=160) of the cut surface. To detect tumor within 2mm of the specimen surface, the sensitivity of optical specimen mapping was 100%. The maximal observed penetration depth of panitumumab-IRDye800 through human tissue in our study was 6.3mm.
Conclusion: Optical specimen mapping is a highly sensitive and specific method for evaluation of margins within <5mm of the tumor mass in HNSCC specimens. This technology has potentially broad applications for ensuring adequate tumor resection and negative margins in head and neck cancers.