ABSTRACT
Optical clearing agents have been investigated mainly for imaging applications in normal tissues, but they have additional potential in cancer diagnosis and therapy. This chapter discusses optical clearing in melanoma using an in vivo model, with topical application of an optical clearing agent. This doubled to ~750 μm the effective depth of high-resolution microvasculature imaging using optical coherence tomography. The use of optical clearing to enhance the treatment depth in photodynamic therapy (PDT) was investigated, in combination with a dual-photosensitizer strategy targeting both the microvasculature and tumor cells. Tumors up to 1 mm in thickness could be eradicated, which represents a significant advance over previous work and opens the possibility of using PDT on melanoma for the first time. These findings may also extend the use of optical clearing to other cancers such as nodular or pigmented basal cell carcinomas and even in tumors of hollow organs using endoscopic and interstitial delivery. First-in-human clinical trials in basal cell carcinoma are in progress. Optical clearing agents represent an inexpensive and safe technique for improving light distribution within tumors, providing enhanced optical imaging and phototherapies.
