Background: Fluorescence imaging hardware (SPY) has recently been developed for intraoperative assessment of blood flow via detection of probes emitting in the near-infrared (NIR) spectrum. This study sought to determine if this imaging system was capable of detecting micrometastatic head and neck squamous cell carcinoma (HNSCC) in preclinical models.
Methods: A NIR fluorescent probe (IRDye800CW) was covalently linked to a monoclonal antibody targeting epidermal growth factor receptor (EGFR; panitumumab) or nonspecific IgG. HNSCC flank (SCC-1) and orthotopic (FADU and OSC19) xenografts were imaged 48-96 h after systemic injection of labeled panitumumab or IgG. The primary tumor and regional lymph nodes were dissected using fluorescence guidance with the SPY system and grossly assessed with a charge-coupled NIR system (Pearl). Histologic slides were also imaged with a NIR charged-coupled device (Odyssey) and fluorescence intensity was correlated with pathologic confirmation of disease.
Results: Orthotopic tongue tumors were clearly delineated from normal tissue with tumor-to-background ratios of 2.9 (Pearl) and 2.3 (SPY). Disease detection was significantly improved with panitumumab-IRDye compared to IgG-IRDye800 (P < 0.05). Tissue biopsy samples (average size 3.7 mm) positive for fluorescence were confirmed for pathologic disease by histology and immunohistochemistry (n = 25 of 25). Biopsy samples of nonfluorescent tissue were proven to be negative for malignancy (n = 28 of 28). The SPY was able to detect regional lymph node metastasis (<1.0 mm) and microscopic areas of disease. Standard histological assessment in both frozen and paraffin-embedded histologic specimens was augmented using the Odyssey.
Conclusions: Panitumumab-IRDye800 may have clinical utility in detection and removal of microscopic HNSCC using existing intraoperative optical imaging hardware and may augment analysis of frozen and permanent pathology.