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

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Summary 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 mol L−1) and irradiated consecutively using either an incoherent halogen lamp (em = 580–750 nm; 24 J cm−2; 40 mW cm−2) or an LED system (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.

Keywords: 5-aminolaevulinic acid; actinic keratoses; photodynamic therapy; protoporphyrin IX

Document Type: Research Article


Publication date: April 1, 2006


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