Simultaneous In Vivo Fluorescent Markers for Perfusion, Protoporphyrin Metabolism, and EGFR Expression for Optically Guided Identification of Orthotopic Glioma

Purpose: While extent of tumor resection is an important predictor of outcome in glioma, margin delineation remains challenging due to lack of inherent contrast between tumor and normal parenchyma. Fluorescence-guided surgery is promising for its ability to enhance contrast through exogenous fluorophores; however, the specificity and sensitivity of the underlying contrast mechanism and tumor delivery and uptake vary widely across approved and emerging agents. Experimental Design: Rats with orthotopic F98 wild-type and F98 EGFR-positive (EGFR(+)) gliomas received in vivo administration of IRDye680RD, 5-aminioleuvulinic acid, and ABY-029-markers of perfusion, protoporphyrin metabolism, and EGFR expression, respectively. Ex vivo imaging demonstrates the contrast mechanism-dependent spatial heterogeneity and enables within-animal comparisons of tumor-to-background ratio (TBR). Results: Generally, ABY-029 outperformed PpIX in F98(EGFR) orthotopic tumor margins and core (50% and 60% higher TBR, respectively). PpIX outperformed ABY-029 in F98(wt) margins by 60% but provided equivalent contrast in the bulk tumor. IRDye680RD provided little contrast, having an average TBR of 1.7 +/- 0.2. The unique spatial patterns of each agent were combined into a single metric, the multimechanistic fluorescence-contrast index (MFCI). ABY-029 performed best in EGFR(+) tumors (91% accuracy), while PpIX performed best in wild-type tumors (87% accuracy). Across all groups, ABY-029 and PpIX performed similarly (80% and 84%, respectively) but MFCI was 91% accurate, supporting multiagent imaging when tumor genotype was unknown. Conclusions: Human use of ABY-029 for glioma resection should enhance excision of EGFR(+) tumors and could be incorporated into current PpIX strategies to further enhance treatment in the general glioma case. (C) 2016 AACR.