Surgical molecular navigation with ratiometric activatable cell penetrating peptide for intraoperative identification and resection of small salivary gland cancers.

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.