title: Dosimetry study of PHOTOFRIN-mediated photodynamic therapy in a mouse tumor model.
abstract: It is well known in photodynamic therapy (PDT) that there is a large variability between PDT light dose and therapeutic outcomes. An explicit dosimetry model using apparent reacted1O2concentration ([1O2]rx) has been developed as a PDT dosimetric quantity to improve the accuracy of the predicted ability of therapeutic efficacy. In this study, this explicit macroscopic singlet oxygen model was adopted to establish the correlation between calculated reacted [1O2]rxand the tumor growth using Photofrin-mediated PDT in a mouse tumor model. Mice with radiation-induced fibrosarcoma (RIF) tumors were injected with Photofrin at a dose of 5 mg/kg. PDT was performed 24h later with different fluence rates (50, 75 and 150 mW/cm2) and different fluences (50 and 135 J/cm2) using a collimated light applicator coupled to a 630nm laser. The tumor volume was monitored daily after PDT and correlated with the total light fluence and [1O2]rx. Photophysical parameters as well as the singlet oxygen threshold dose for this sensitizer and the RIF tumor model were determined previously. The result showed that tumor growth rate varied greatly with light fluence for different fluence rates while [1O2]rxhad a good correlation with the PDT-induced tumor growth rate. This preliminary study indicated that [1O2]rxcould serve as a better dosimetric predictor for predicting PDT outcome than PDT light dose.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104; Department of Laser Medicine, Chinese PLA General Hospital, Beijing, 100853.
authors.forename: Haixia
authors.initials: H
authors.lastname: Qiu
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104; Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Michele M
authors.initials: MM
authors.lastname: Kim
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Rozhin
authors.initials: R
authors.lastname: Penjweini
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA 19104.
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Zhu
keywords: Photofrin; explicit PDT dosimetry; macroscopic singlet oxygen model; photodynamic therapy