It is likely that the higher levels of soluble circulating CEA in animals with larger tumor burdens (Figure 2) may have led to more formation of 177Lu-DOTA-M5A:CEA complexes, resulting in higher uptake in the liver (approximately 32%ID/g at 96 h post-injection) than in animals with smaller tumors. This evidence concerns the gene CEACAM5 and neoplasm.