In vitro and in vivo comparison of two different light sources for topical photodynamic therapy

Br J Dermatol. 2006 Apr;154(4):712-8. doi: 10.1111/j.1365-2133.2006.07143.x.


Background: Photodynamic therapy (PDT) with 5-aminolaevulinic acid (ALA) is an effective and safe treatment option for the treatment of actinic keratosis (AK). Incoherent lamps are often used, matching the absorption maxima of ALA.

Objectives: A comparative trial was performed to evaluate the efficacy of recently developed light-emitting diodes (LEDs).

Methods: Human epidermal keratinocytes were incubated for 24 h with ALA (100, 200, 300, 400 or 500 micromol L(-1)) and irradiated consecutively using either an incoherent halogen lamp (lambda(em) = 580-750 nm; 24 J cm(-2); 40 mW cm(-2)) or an LED system (lambda(em) = 633 +/- 3 nm; 3, 6, 12 or 24 J cm(-2); 40 mW cm(-2)). Topical ALA-PDT was performed on 40 patients with AK (n = 584) in a symmetrical distribution suitable for two-sided comparison. After incubation with ALA (20% in cream base) irradiation was performed with the incoherent lamp (100 J cm(-2); 160 mW cm(-2)) on one side and the LED system (40 J cm(-2); 80 mW cm(-2)) on the opposite side followed by re-evaluation up to 6 months.

Results: No significant differences between the LED system (3, 6, 12 or 24 J cm(-2)) and the incoherent light source (24 J cm(-2)) regarding cytotoxicity was found in vitro. The complete remission rate yielded in the in vivo investigation was also not significantly different at 6 weeks (P = 0.95), 3 months (P = 0.75) and 6 months (P = 0.61) following therapy. Six weeks following therapy complete remission rates of 84.3% (LED system) and 82.8% (incoherent lamp) were achieved. There was also no significant difference between both light sources regarding pain during light treatment (P = 0.67), patient satisfaction (P = 1.0) or cosmesis (P = 1.0) following therapy.

Conclusions: These results show the efficacy of an LED system for ALA-PDT both in vitro and in vivo. ALA-PDT with the LED system showed a noninferiority regarding the clinical outcome in the treatment of AK compared with the incoherent lamp.

Publication types

  • Comparative Study
  • Controlled Clinical Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aminolevulinic Acid / therapeutic use
  • Cell Survival / drug effects
  • Cell Survival / radiation effects
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Female
  • Humans
  • Keratinocytes / drug effects
  • Keratinocytes / radiation effects*
  • Keratosis / drug therapy*
  • Keratosis / pathology
  • Lighting / instrumentation*
  • Male
  • Middle Aged
  • Pain / etiology
  • Photochemotherapy / adverse effects
  • Photochemotherapy / instrumentation*
  • Photosensitizing Agents / therapeutic use
  • Treatment Outcome


  • Photosensitizing Agents
  • Aminolevulinic Acid