Introduction: Oral squamous cell carcinoma (OSCC) remains a leading contributor to overall head and neck malignancy. In recent years, cancer-specific fluorescent imaging targets have been used to aid in the diagnosis, delineation, and resection of various tumor types. Despite their success, criticism has emphasized the futility of intravenous injection of these agents. This study analyzes the effectiveness of topical application of three injectable fluorescent agents in the diagnosis and delineation of OSCC. Agents of focus include cetuximab IRDye-800CW, a fluorescently-labeled epidermal growth factor receptor (EGFR) inhibitor, Integrisense 750, a fluorochrome and integrin αvβ3 antagonist, and Prosense 750EX, a fluorescent agent activated by tissue proteases.
Methods: A xenograft model was created by injecting the dorsum of nude athymic mice with luciferase-positive cells from the UM-SCC-1 cell line. After a 72 hour incubation period, dorsal soft tissue flaps were elevated and removed. Soft tissue flaps were imaged to verify bioluminescence at the site of each injected tumor. We then topically applied each of the above fluorescent imaging agents individually to single soft tissue tumor flaps (n=6). Flaps were then imaged to assess specific fluorescent values; optimal agent concentrations and imaging time points were determined. Final images were obtained after the soft tissue flaps were washed with phosphate-buffered saline (PBS). Blocking studies were performed to explore target specificity for cancer cells versus non-cancerous background. Student’s t-tests were used to analyze numerical data.
Results: Maximum pre-wash mean tumor-to-background ratio (TBR) using cetuximab IRDye-800CW was achieved with 2 mg/mL concentration at time 16 minutes (TBR=1.11). Washing the soft tissue flaps with PBS reliably and significantly improved tumor delineation compared to background. There was a 2.54% decrease in mean TBR after prior application of unlabeled EGFR inhibitor.
In the Integrisense 750 group, maximum mean TBR occurred at 0 minutes with a concentration of 61 ng/mL (TBR=1.98). Washing the soft tissue flap did not have a reliably significant effect on tumor delineation. There was a 25.3% decrease in mean TBR after prior application of unlabeled integrin αvβ3 antagonist.
In the Prosense 750EX group, maximum mean TBR occurred at 16 minutes with a concentration of 30.5 ng/mL (TBR=0.964). Washing the tumor flap did not reliably affect tumor delineation. Interestingly, there was a 15% increase in TBR with prior application of unlabeled pan-cathepsin antibody.
Conclusion: Cetuximab IRDye-800CW and Integrisense 750 show promise for topically-based application and the enhanced ability to assess for OSCC. To assess tumors using topically-applied cetuximab IRDye-800CW, this agent should be applied at a concentration of 2 mg/mL, tumors should be allowed to rest in solution for 16 minutes, and the site of interest should be washed with saline prior to fluorescent imaging. When assessing tumors while using topically-applied Integrsense 750, fluorescent imaging should be performed immediately after application of agent without a preceding saline wash. Together, these agents represent a unique, noninvasive technique for improving the identification of dysplastic and neoplastic lesions in patients with true OSCC.