title: The relationship of phthalocyanine 4 (pc 4) concentrations measured noninvasively to outcome of pc 4 photodynamic therapy in mice.
abstract: The ability to noninvasively measure photosensitizer concentration at target tissues will allow optimization of photodynamic therapy (PDT) and could improve outcome. In this study, we evaluated whether preirradiation tumor phthalocyanine 4 (Pc 4) concentrations, measured noninvasively by the optical pharmacokinetic system (OPS), correlated with tumor response to PDT. Mice bearing human breast cancer xenografts were treated with 2 mg kg(-1) Pc 4 iv only, laser irradiation (150 J cm(-2)) only, Pc 4 followed by fractionated irradiation or Pc 4 followed by continuous irradiation. Laser irradiation treatment was initiated when the tumor to skin ratio of Pc 4 concentration reached a maximum of 2.1 at 48 h after administration. Pc 4 concentrations in tumor, as well as in Intralipid in vitro, decreased monoexponentially with laser fluence. Pc 4-PDT resulted in significant tumor regression, and tumor response was similar in the groups receiving either fractionated or continuous irradiation treatment after Pc 4. Tumor growth delay following Pc 4-PDT correlated with OPS-measured tumor Pc 4 concentrations at 24 h prior to PDT (R2=0.86). In excised tumors, OPS-measured Pc 4 concentrations were similar to the HPLC-measured concentrations. Thus, OPS measurements of photosensitizer concentrations can be used to assist in the scheduling of Pc 4-PDT.
authors.affiliation: Department of Pharmacology and Chemical Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Lihua
authors.initials: L
authors.lastname: Bai
authors.forename: Jianxia
authors.initials: J
authors.lastname: Guo
authors.forename: Franklin A
authors.initials: FA
authors.lastname: Bontempo
authors.forename: Julie L
authors.initials: JL
authors.lastname: Eiseman