|
|
|
| Abstract Title:
|
| Monitoring and Modeling Topical ALA PDT of Nodular Basal Cell Carcinomas
|
| Graduate Student Presenter:
|
Theresa Sands
|
| Name of the Author(s) and Affiliation(s):
|
Theresa Sands, IGERT, Roswell Park Cancer Institute; Ulas Sunar, Roswell Park Cancer Institute; Thomas Foster, University of Rochester; Allan Oseroff, Roswell Park Cancer Institute.
|
Photodynamic therapy (PDT) is used to treat cancer. It involves giving a photosensitizer (PS) then illuminating the area. Photofrin is commonly used. A drawback of using Photofrin is it causes photosensitivity for weeks. Aminolevulinic Acid (ALA) is a precursor in the heme biosynthesis pathway. The penultimate step in this pathway is the photosensitizer protoporphyrin IX (PpIX). Normally, PpIX doesn't accumulate due to a feedback mechanism but if ALA is added, this mechanism can be overcome. PpIX is rapidly converted to the heme, preventing prolonged photosensitivity. Topical application of ALA is possible and this method further reduces the toxicity to normal tissues.
PDT works by exciting ground state triplet oxygen to singlet oxygen, which causes cellular damage. As well as light and PS, oxygen is needed for PDT. If light is applied at a high irradiance, the oxygen in the tissue may be depleted. Also, the blood vessels may temporarily shut down during high irradiance.
Although ALA PDT is effective in treating superficial carcinomas it is less effective for nodular basal cell carcinomas (nBCCs). This limitation is not fully understood. The objective of this study is to better understand why PDT of nBCCs is less successful. The areas to be explored are: PpIX penetration through the depth of the tumor, the vasculature characteristics and spacings of nBCCs, vascular perfusion of nBCCs during PDT, and photobleaching dynamics of PpIX in nBCCs during PDT. This information can be incorporated into models to predict more effective light delivery regimens.
|
|
|
