Evaluation of Photodynamic Therapy near Functional Brain Tissue in Patients with Recurrent Brain Tumors

AbstractIntroduction: Photodynamic therapy (PDT) involves the selective retention of a photosensitizer that upon activation with light mediates tumor cell destruction via the production of singlet oxygen. This study evaluates the toxicity of PDT and a new light-delivery device based on light-emitting diode (LED) technology in selected patients with brain tumors. Methods: Twenty patients with recurrent malignant brain tumors received 22 treatments with PDT. Sixteen tumors were supratentorial and four tumors were infratentorial. Patients received IV Photofrin® 24 h prior to light exposure starting at 0.75 mg kg-1. Laser and LED arrays were used to deliver 100 J cm-2 of light to the sensitized tumors. Fourteen patients received PDT with a laser-balloon adapter, two via interstitial optical fibers and five patients had LED based PDT. At the maximum Photofrin® dose of 2.0 mg kg-1 five patients received laser-balloon adapter light and five patients received LED light. In addition, three patients received LED light with 0.25 mg kg-1 of Visudine®, a benzoporphyrin derivative (BPD). Quantitative analysis of toxicity and time to progression was performed. Results: Two patients had toxicity consisting of ataxia and facial weakness after treatment with interstitial fibers. Escalating doses of Photofrin® were tolerated to the maximum dose of 2.0 mg kg-1. BPD did not result in additional toxicity. PDT in the posterior fossa or near eloquent brain was tolerated using the LED or laser-balloon adapter. All patients had tumor responses as documented by MRI scan and the mean time to tumor progression after PDT was 67 weeks. Conclusion: PDT with LED balloon adapters (also tunable dye laser) has acceptable toxicity in brain tumor patients. Future studies using more effective photosensitizers could improve local recurrence control.