title: In vitro photodynamic therapy of human lung cancer: investigation of dose-rate effects.
abstract: The influence of light dose-rate delivery was studied in human lung adenocarcinoma A549 cells treated with hematoporphyrin derivative (Photofrin II)-based photodynamic therapy. Clonogenic cell survival curves were generated for cells treated for 2 h with 25 micrograms/ml of Photofrin II followed by exposure to light delivered at 0.3, 0.15, 0.075, or 0.0375 milliwatts/cm2. Cellular sensitizer levels, as determined by fluorescence measurements, remained constant over the entire time course of all light exposures. As the dose rate of light delivery was decreased, a significant increase in cell survival was observed at equal light energies (225 mJ/cm2). The enhancement in survival from the highest to the lowest dose rate used was 1.6-fold (at the 50% survival level). These findings may have important clinical implications relating to photodynamic therapy of tumors and may provide a partial explanation for treatment failure.
authors.affiliation: Thoracic Oncology Section, National Cancer Institute, Bethesda, Maryland 20892.
authors.forename: W
authors.initials: W
authors.lastname: Matthews
authors.forename: J
authors.initials: J
authors.lastname: Cook
authors.forename: J B
authors.initials: JB
authors.lastname: Mitchell
authors.forename: R R
authors.initials: RR
authors.lastname: Perry
authors.forename: S
authors.initials: S
authors.lastname: Evans
authors.forename: H I
authors.initials: HI
authors.lastname: Pass
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000473:pathology*; D002470:Cell Survival / Q000187:drug effects; D005453:Fluorescence; D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins / Q000627:therapeutic use*; D006801:Humans; D008027:Light; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology*; D010778:Photochemotherapy; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: D006415:Hematoporphyrins; D017324:Hematoporphyrin Derivative