Detection of colon cancer metastases with fluorescence laparoscopy in orthotopic nude mouse models

Objective: To improve detection of colon cancer metastases using fluorescence laparoscopy (FL). Design: An orthotopic mouse model of human colon cancer was established by intracecal injection of HCT-116 human colon cancer cells expressing green fluorescent protein into 12 mice. One group modeled early disease and the second modeled late metastatic disease. For the early-disease model, 2 weeks after implantation, 6 mice underwent 2 modalities of laparoscopy: bright field laparoscopy (BL) and FL. The number of metastases identified within each of the 4 abdominal quadrants was recorded with both laparoscopy modalities. This process was repeated in the latemetastatic disease group 4 weeks after implantation. All animals were then humanely sacrificed and imaged using open fluorescence laparoscopy (OL) as a positive control to identify metastases. Setting: Basic science laboratory. Participants: Twelve female, 6-week-old nude mice. Interventions: Detection of tumor foci by FL compared with BL. Main Outcome Measures: Number of tumors identified in each quadrant. Results: Fluorescence laparoscopy enabled superior visualization of colon cancer metastases compared with BL in the early (P=.03) and late (P=.002) models of colon cancer. Compared with OL, BL was significantly inferior in the early (P=.04) and late (P<.001) groups. Fluorescence laparoscopy was not significantly different from OL in the early (P=.85) or late (P=.46) group. Thus, FL allowed identification of micrometastases that could not be distinguished from surrounding tissue using BL. Conclusions: The use of FL enables identification of metastases that could not be visualized using standard laparoscopy. This report illustrates the important clinical potential for FL in the surgical treatment of cancer.