Fluorescent antibody tagging of colon cancer in the nude mouse; a model for improved surgical accuracy in the oncologic patient

13501 Background: Induced fluorescence of malignant tumors has the potential to improve the surgeon’s ability to accurately identify and excise all malignant tissue. Tumors can be made fluorescent using fluorophore-tagged anti-tumor antigen antiboies. We present here our results using a human colon cancer cell line in the nude mouse model. Methods: HCT 116 colon cancer cells were subcutaneously or orthotopically implanted in 16 nude mice (12 study mice and 4 control mice). Two to 8 weeks after injection, tumor nodules were easily detectable. Using the tail vein method, all mice were injected with fluorophore-tagged anti-CEA or fluorophore-tagged IgG. Mice were examined using a small animal imaging system with a 470 nm light source and appropriate filters. They were also examined using a simple blue LED flashlight fitted with a fixed 470 nm band pass filter for illumination and were observed through filtered goggles. Results: All tumor nodules in the study mice demonstrated green fluorescence when visualized through the skin. On dissection and exposure of the tumor nodules, this fluorescence was intense and clearly distinguishable from the surrounding normal tissue using either the imaging system or the blue LED. Very small (<0.5mm) metastatic nodules were easily identified. Bright tumor fluorescence remained visible up to 5 days after injection. Control mice injected with fluorophore-tagged IgG and examined in a similar manner revealed no tumor fluorescence. Minimal non-specific dull fluorescence was occasionally observed in gut mucosa and ovarian tissue but was easily distinguished from the bright tumor fluorescence. Conclusions: When tumor surface antigens are known and antibodies to those antigens are available, this technology is simple, easy to perform, requires no technically complex equipment or operator expertise and could be readily adapted for cancer surgery in the academic or community hospital setting. Major indications for this technology would be in those patients where tumor resection offers an excellent chance for cure or significantly improves survival. The implications for increased accuracy of procedures such as resection of primary colorectal cancer or resection of solitary hepatic or pulmonary metastases are clear. No significant financial relationships to disclose.