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


OBJECTIVE
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.
Babilas
P
P
Department of Dermatology, University of Regensburg, Regensburg, Germany. philipp.babilas@klinik.uni-regensburg.de
Kohl
E
E
Maisch
T
T
Bäcker
H
H
Gross
B
B
Branzan
A L
AL
Bäumler
W
W
Landthaler
M
M
Karrer
S
S
Szeimies
R-M
RM
D000328:Adult; D000368:Aged; D000622:Aminolevulinic Acid / Q000627:therapeutic use; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000528:radiation effects*; D007642:Keratosis / Q000188:drug therapy* / Q000473:pathology; D008029:Lighting / Q000295:instrumentation*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology; D010778:Photochemotherapy / Q000009:adverse effects / Q000295:instrumentation*; D017319:Photosensitizing Agents / Q000627:therapeutic use; D016896:Treatment Outcome
D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid