Advances in contrast agents, reporters, and detection

Abstract

The use of exogenous probes to gain a deeper understanding of physiological and molecular processes in vivo through the acquisition of optical signals, particularly via enhanced contrast using molecular probes (physiologically transported, site-directed, or via reporter genes) has emerged with tremendous vigor in the past few years. One such area of expanded activity is in the area of early cancer detection, in great part because it is so critical to the clinical outcome in the treatment.^{1 2 3} As an example, in colon cancer, which accounts for 15 of all U.S. cancer-related deaths, only 37 are found early enough for moderate treatment¹ and once these types of cancer reach metastatic activity the survival rate is only 7. Oral and brain cancer represent other examples where a need exists for early detection or improved imaging during treatment. Each year about 31 000 Americans develop oral cancer. Squamous cell carcinoma (SCC) accounts for 95 of all malignant oral lesions with SCC having a survival rate of only 50. Yet when this type of cancer is detected in its earliest stages, the survival rate becomes approximately 80.⁴ In cancers of the esophagus, the five-year survival rate is only listed at 5. In contrast, if these cancers are detected when it is still contained in the mucosa the five-year survival rate becomes 90.⁵ For brain cancer the survival rate is abysmal—less than 2 years for younger patients and just weeks for those that are older—and is critically dependent on the imaging technique used during treatment.⁶