Image-guided tumor resection using real-time near-infrared fluorescence in a syngeneic rat model of primary breast cancer
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Tumor involvement of resection margins is found in a large proportion of patients who undergo breast-conserving surgery. Near-infrared (NIR) fluorescence imaging is an experimental technique to visualize cancer cells during surgery. To determine the accuracy of real-time NIR fluorescence imaging in obtaining tumor-free resection margins, a protease-activatable NIR fluorescence probe and an intraoperative camera system were used in the EMR86 orthotopic syngeneic breast cancer rat model. Influence of concentration, timing and number of tumor cells were tested in the MCR86 rat breast cancer cell line. These variables were significantly associated with NIR fluorescence probe activation. Dosing and tumor size were also significantly associated with fluorescence intensity in the EMR86 rat model, whereas time of imaging was not. Real-time NIR fluorescence guidance of tumor resection resulted in a complete resection of 17 out of 17 tumors with minimal excision of normal healthy tissue (mean minimum and a mean maximum tumor-free margin of 0.2 ± 0.2 mm and 1.3 ± 0.6 mm, respectively). Moreover, the technique enabled identification of remnant tumor tissue in the surgical cavity. Histological analysis revealed that the NIR fluorescence signal was highest at the invasive tumor border and in the stromal compartment of the tumor. In conclusion, NIR fluorescence detection of breast tumor margins was successful in a rat model. This study suggests that clinical introduction of intraoperative NIR fluorescence imaging has the potential to increase the number of complete tumor resections in breast cancer patients undergoing breast-conserving surgery.
KeywordsNear-infrared fluorescence imaging Image-guided surgery Breast conserving surgery Incomplete tumor resection Cathepsin
Formalin fixed paraffin embedded
We want to thank Rob Keyzer and Anita Sajet for technical assistance and Fluoptics (Grenoble, France) for use of the Fluobeam® system. J.S.D. Mieog is a MD-medical research trainee funded by The Netherlands Organisation for Health Research and Development (grant nr. 92003526).
Online Resource 1—Time-dependent activation of ProSense680 by MCR86 breast cancer rat cells: Fluorescence microscopy (LSM510 Zeiss confocal microscope, 40x objective) of a cluster of MCR86 cells. Images were acquired directly after incubation with ProSense680 (33.3 nM) up to 4.5 h thereafter. (MPG 1894 kb)
Online Resource 2—Intraoperative NIR fluorescence image-guided resection of primary breast cancer: Movie showing NIR fluorescence signal registered by the Fluobeam intraoperative camera system. Shown is a resection of an EMR86 tumor in a female WAG/Rij rat 24 h after intravenous administation of 10 nmol ProSense680. (MPG 6262 kb)
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