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.

Conclusion:

Large-surface topical ALA–PDT with blue light can delay the appearance of UV-induced actinic keratoses and squamous cell carcinoma in hairless mice.