Fluorescence-guided surgery with a fluorophore-conjugated antibody to carcinoembryonic antigen (CEA), that highlights the tumor, improves surgical resection and increases survival in orthotopic mouse models of human pancreatic cancer

Abstract

Background: We have developed a method of distinguishing normal tissue from pancreatic cancer in vivo using fluorophore-conjugated antibody to carcinoembryonic antigen (CEA). The objective of this study was to evaluate whether fluorescence-guided surgery (FGS) with a fluorophore-conjugated antibody to CEA, to highlight the tumor, can improve surgical resection and increase disease-free survival (DFS) and overall survival (OS) in orthotopic mouse models of human pancreatic cancer.

Methods: We established nude-mouse models of human pancreatic cancer with surgical orthotopic implantation of the human BxPC-3 pancreatic cancer. Orthotopic tumors were allowed to develop for 2 weeks. Mice then underwent bright-light surgery (BLS) or FGS 24 h after intravenous injection of anti-CEA-Alexa Fluor 488. Completeness of resection was assessed from postoperative imaging. Mice were followed postoperatively until premorbid to determine DFS and OS.

Results: Complete resection was achieved in 92 % of mice in the FGS group compared to 45.5 % in the BLS group (p = 0.001). FGS resulted in a smaller postoperative tumor burden (p = 0.01). Cure rates with FGS compared to BLS improved from 4.5 to 40 %, respectively (p = 0.01), and 1-year postoperative survival rates increased from 0 % with BLS to 28 % with FGS (p = 0.01). Median DFS increased from 5 weeks with BLS to 11 weeks with FGS (p = 0.0003). Median OS increased from 13.5 weeks with BLS to 22 weeks with FGS (p = 0.001).

Conclusions: FGS resulted in greater cure rates and longer DFS and OS using a fluorophore-conjugated anti-CEA antibody. FGS has potential to improve the surgical treatment of pancreatic cancer.

Conflict of interest statement

Disclosure: The authors declare no conflict of interest.

Figures

Fig. 1

Study schema. Two weeks after implantation, the mice were randomized to 1 of 4 treatment groups: control (no treatment), GEM only, BLS with adjuvant GEM, or FGS with adjuvant GEM. Tumors were resected using the MVX-10 microscope. Starting on postoperative day 0, all mice from each surgical arm underwent 4 weeks of GEM treatment. GEM treatment was started 2 weeks after implantation of tumor fragments in the GEM-only group and continued for 4 weeks. All 73 mice were followed postoperatively and imaged weekly using the OV-100. When premorbid, the mice were humanely sacrificed for open imaging

Fig. 2

Pre- and postoperative tumor burden. Representative OV-100 images are shown of a mouse from the FGS group with the tail of the pancreas and spleen delivered through a midline incision. From left to right, images were taken under bright field (BF), or using the following filters: a GFP filter (excitation 460–490 nm, emission 510 nm long-pass); a GFPa filter (excitation 460–490 nm, emission 510–550 nm); and an RFP filter (excitation 535–555 nm, emission 570–623 nm). With the GFPa filter, only the AlexaFluor 488 bound to CEA is visualized. The RFP filter only permits visualization of the tumor expressing RFP. Under the GFP filter, both AlexaFluor 488- and the RFP-expressing tumor are simultaneously visualized, giving a yellow color. The high correlation of red and green indicates high specificity of the green fluorophore-labeled anti-CEA antibody

Fig. 3

Disease-free survival (DFS). There was a significant difference in DFS between the 2 surgical groups (p < 0.0001). Mice in the FGS group had a median DFS of 11 weeks compared to 5 weeks in the BLS group. Tumor never regressed in the other two treatment groups, and they were therefore excluded from this plot

Fig. 4

Overall survival (OS). OS did not significantly differ between the control group, the GEM-only group, and the BLS+GEM group. However, FGS+GEM significantly lengthened OS in the mouse models of human pancreatic cancer (p = 0.003)