M. Tabata1, N. Nathan1, T. Teraphongphom1, K. Hettie2, J. Klockow2, S. Rogalla3, R. Ertsey1, E. Rosenthal1,2 2Stanford University,Radiology,Stanford, CA, USA 3Stanford University,Pediatrics,Palo Alto, CA, USA 1Stanford University,Otolaryngology – Head And Neck Cancer,Palo Alto, CA, USA
Introduction: Despite widespread acceptance of fluorescence imaging for several different types of cancer, the ideal optical imaging probe for intraoperative delineation of head and neck squamous cell carcinoma (HNSCC) margins has not yet been identified. Identification of this probe for detecting subclinical disease in tumor margins will improve oncologic surgical outcomes. This study compares a fluorescently labeled anti-epidermal growth factor receptor (EGFR) antibody, Cetuximab-IRDye800CW (IR800-CTM), with an ultra pH-sensitive (UPS) fluorescent nanoprobe for detection of HNSCC.
Methods: Thirteen immunodeficient mice were inoculated with HCT. Through tail vein injections, four mice were given 200 uL of IR800-CTM at 14uM. Three were given 100 uL of UPS nanoprobes, and three were given 200 uL, both at 0.1 mg/mL. Two were given 200 uL of saline, and one was given 200 uL of IRDye800 at 28uM. Images were acquired using the Pearl® Trilogy(LI-COR) in vivo optical imaging system at 8, 22, 26, 30, 46, and 72 hours along with the SPY Elite®(Novadaq) at 72 hours. Ex vivo images were acquired using the Pearl® and Odyssey®(LI-COR). Tumor to background ratios (TBR) were calculated by dividing the intensity of the fluorescence in the tumor by that of healthy flank tissue. TBRs of the UPS nanoprobe group and the IR800-CTM group were compared. An unpaired, two-sided Student’s T-test with unequal variance was used to test for statistical significance.
Results: There is no statistically significant difference between TBRs of UPS nanoprobes and IR800-CTM in vivo. We can successfully image tumors in vivo and obtain TBRs of 2.81 (±0.68 SD) with UPS nanoprobes and 5.27 (±1.85 SD) with IR800-CTM. Ex vivo histology confirms fluorescence in tumors. The TBR of the UPS nanoprobes reached a maximum at 22 hours and stayed above 83% of maximum until 72 hours. The lower dose of 100µL yields stronger and more specific signal than the 200µL dose. Both UPS nanoprobes and IR800-CTM localize in kidneys and liver, and IR800-CTM shows greater tumor:liver fluorescence ratio.
Conclusion: Both UPS nanoprobes and IR800-CTM are tools for intraoperative optical visualization of cancer. The earlier TBR peak of UPS nanoprobes is clinically advantageous. Currently, complete removal of HNSCC with minimal damage to other tissues cannot be guaranteed, and improved visualization of tumor margins would improve post-surgery oncologic outcomes. We compare two methods for optical imaging of tumor margins in HNSCC. These outcomes will help guide further investigation of an optimal optical imaging agent for HNSCC. This methodology is reproducible for investigation in other tumor types.
