Both anti-VEGFR (bevacizumab) [103] and anti-carcinoembryonic antigen (CEA) [57,104], conjugated to a fluorescent dye, showed suboptimal signal-to-background ratios, ranging from 1.4 to 2.1 when tested on patients with pancreatic and colorectal cancer. This evidence concerns the gene CEACAM5 and colorectal cancer.