Tumor-specific fluorescence antibody imaging enables accurate staging laparoscopy in an orthotopic model of pancreatic cancer

Abstract

Background/aims: Laparoscopy is important in staging pancreatic cancer, but false negatives remain problematic. Making tumors fluorescent has the potential to improve the accuracy of staging laparoscopy.

Methodology: Orthotopic and carcinomatosis models of pancreatic cancer were established with BxPC-3 human pancreatic cancer cells in nude mice. Alexa488-antiCEA conjugates were injected via tail vein 24 hours prior to laparoscopy. Mice were examined under bright field laparoscopic (BL) and fluorescence laparoscopic (FL) modes. Outcomes measured included time to identification of primary tumor for the orthotopic model and number of metastases identified within 2 minutes for the carcinomatosis model.

Results: FL enabled more rapid and accurate identification and localization of primary tumors and metastases than BL. Using BL took statistically significantly longer time than FL (p<0.0001, fold change and 95% CI for BL vs. FL: 8.12 (4.54,14.52)). More metastatic lesions were detected and localized under FL compared to BL and with greater accuracy, with sensitivities of 96% vs. 40%, respectively, when compared to control. FL was sensitive enough to detect metastatic lesions <1mm.

Conclusions: The use of fluorescence laparoscopy with tumors labeled with fluorophore-conjugated anti-CEA antibody permits rapid detection and accurate localization of primary and metastatic pancreatic cancer in an orthotopic model. The results of the present report demonstrate the future clinical potential of fluorescence laparoscopy.

FIGURE 1

Time to identify primary tumor in the body of the pancreas. Images under fluorescence and bright field laparoscopy demonstrating the primary tumor in the body of the pancreas. The two images on the left (A,C) are OV-100 positive control images for comparison with laparoscopic images on the right (B,D) under fluorescence (top) and bright field (bottom). The primary pancreatic tumor was more easily detected under fluorescence compared to bright field. (E) Under bright field laparoscopy (BL), the average duration was 63.1±13.94 seconds vs. 9.45±1.81 seconds under fluorescence laparoscopy (FL) (p=0.003).

FIGURE 2

Use of fluorescence laparoscopy to identify primary and metastatic lesions. The center image is a positive control OV-100 image for comparison with BL and FL. The surrounding images, labeled 1–6, are representative FL images of primary and metastatic pancreatic tumor lesions. The numbers in the upper left corner of each outer panel corresponds with the numbered lesion in the centered OV-100 panel.

FIGURE 3

Histological confirmation of tumors visualized by FL. (A) Small fluorescent foci on the peritoneal surface of the bowel (white arrows) visualized during fluorescence laparoscopy. (B,C) Ex vivo visualization of small tumor foci, previously seen during fluorescence laparoscopic imaging using bright field (B) and fluorescence (C) light. The hatched box indicates the segment of tissue analyzed by histology (scale bar=2mm) (D). Composite image showing small focus of tumor (arrow) lodged within the bowel mesentery, corresponding to the fluorescent focus seen within the hatched box in panel (C). This paraffin section was cut in a plane parallel to the images shown in panels (B) and (C) (scale bar=2mm). (E) High magnification view of tumor focus indicated in panel (D) (scale bar=200µm).