title: Multiple large-surface photodynamic therapy sessions with topical or systemic aminolevulinic acid and blue light in UV-exposed hairless mice.
abstract: BACKGROUND
  The use of photodynamic therapy (PDT) with topical aminolevulinic acid (ALA) on large skin surfaces has recently been reported for patients with multiple actinic keratoses.
  
  
  OBJECTIVE
  The current study compared the ability of topical and systemic ALA-PDT as well as topical ALA-PDT with blue light to delay the appearance of UV-induced skin cancer using the hairless mouse as a model.
  
  
  METHODS
  Groups of hairless mice were exposed daily to UV radiation and weekly to ALA-PDT. Tumor-free survival was compared for mice exposed to UV and treated weekly with ALA-PDT and mice exposed only to UV radiation.
  
  
  RESULTS
  Weekly topical or systemic ALA-PDT was able to delay the induction of skin tumors. A significant difference in tumor-free survival was also observed for both actinic keratoses and invasive squamous cell carcinoma in mice treated weekly with topical ALA-PDT performed with blue light. This was observed even when weekly ALA-PDT was started after 8 weeks of UV exposure.
  
  
  CONCLUSIONS
  Large-surface topical ALA-PDT with blue light can delay the appearance of UV-induced actinic keratoses and squamous cell carcinoma in hairless mice.
authors.affiliation: Division of Dermatology, University of Montreal Hospital Centre, Montreal, Quebec, Canada.
authors.forename: Younan
authors.initials: Y
authors.lastname: Liu
authors.forename: Gilles
authors.initials: G
authors.lastname: Viau
authors.forename: Robert
authors.initials: R
authors.lastname: Bissonnette
mesh_terms: D000287:Administration, Topical; D000622:Aminolevulinic Acid / Q000008:administration & dosage*; D000818:Animals; D005260:Female; D007274:Injections, Intraperitoneal; D051379:Mice; D008812:Mice, Hairless; D009381:Neoplasms, Radiation-Induced / Q000517:prevention & control*; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D012867:Skin / Q000528:radiation effects; D012878:Skin Neoplasms / Q000517:prevention & control*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid