Background: We evaluated the use of intraoperative fluorescence guidance by enzymatically cleavable ratiometric activatable cell-penetrating peptide (RACPPPLGC(Me)AG) containing Cy5 as a fluorescent donor and Cy7 as a fluorescent acceptor for salivary gland cancer surgery in a mouse model.
Methods: Surgical resection of small parotid gland cancers in mice was performed with fluorescence guidance or white light (WL) imaging alone. Tumor identification accuracy, operating time, and tumor-free survival were compared.
Results: RACPP guidance aided tumor detection (positive histology in 90% [27/30] vs 48% [15/31] for WL; p < .001). An approximate 25% ratiometric signal increase as the threshold to distinguish between tumor and adjacent tissue, yielded >90% detection sensitivity and specificity. Operating time was reduced by 54% (p < .001), and tumor-free survival was increased with RACPP guidance (p = .025).
Conclusion: RACPP provides real-time intraoperative guidance leading to improved survival. Ratiometric signal thresholds can be set according to desired detection accuracy levels for future RACPP applications.
Keywords: fluorescence-guided surgery; long-term survival; molecular imaging; molecular navigation; ratiometric activatable cell-penetrating peptide (RACPP).
© 2015 Wiley Periodicals, Inc.