Photodynamic Therapy (PDT) for Recurrent Pediatric Brain Tumors

Plain-language summary

The goal of this proposal is to evaluate a new Photodynamic Therapy (PDT) modification which could revolutionize the treatment of brain tumors in children and adults. There are currently few cases published involving the use of PDT in infratentorial (in the posterior fossa) brain tumors in general and specifically those occurring in children. The investigators propose to test a technique, for the first time in the U.S., that demonstrated in Australian adult glioblastoma patients dramatic long-term, survival rates of 57% (anaplastic astrocytoma) and 37% (glioblastoma multiforme). These results are unprecedented in any other treatment protocol. Photodynamic therapy (PDT) is a paradigm shift in the treatment of tumors from the traditional resection and systemic chemotherapy methods. The principle behind photodynamic therapy is light-mediated activation of a photosensitizer that is selectively accumulated in the target tissue, causing tumor cell destruction through singlet oxygen production. Therefore, the photosensitizer is considered to be the first critical element in PDT procedures, and the activation procedure is the second step. The methodology used in this proposal utilizes more intensive laser light and larger Photofrin photosensitizer doses than prior PDT protocols in the U.S. for brain tumor patients. The PDT will consist of photoillumination at 630 nm beginning at the center of the tumor resection cavity, and delivering a total energy of 240 J cm-2. The investigators feel that the light should penetrate far enough into the tissue to reach migrating tumor cells, and destroy these cells without harming the healthy cells in which they are dispersed. The investigators will be testing the hypothesis that pediatric subjects with progressive/recurrent malignant brain tumors undergoing PDT with increased doses of Photofrin® and light energy than were used in our previous clinical study will show better progression free survival (PFS) and overall survival (OS) outcomes. PDT will also be effective against infratentorial tumors. The specific aims include determining the maximum tolerable dose (MTD) of Photofrin in children and looking for preliminary effectiveness trends.

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