Do pulsed lasers produce an effective photodynamic therapy response?
BACKGROUND
Photodynamic therapy (PDT) in dermatology is traditionally performed with topical aminolevulinic acid (ALA) and continuous-wave (CW) illumination with blue or red light. Recently, several authors have reported success with laser and other pulsed-light sources for PDT. While the clinical benefits on sun-exposed skin are apparent, no study has demonstrated that the pulsed light sources are responsible for the observed response.


METHODS
A placebo-controlled study of two pulsed light sources previously reported for PDT: the pulsed dye laser (PDL) or broadband flashlamp filtered intense pulsed light (IPL). Sun-hidden skin was prepared with microdermabrasion and acetone scrub followed by ALA under occlusion. Laser or IPL was delivered under conditions previously reported to produce a clinical response. Control areas were exposed to standardized CW blue light or to no light. A second control area was prepared and received light and the ALA vehicle.


RESULTS
IPL and PDL demonstrated a faint dose-response effect on PDT activation, but were less potent than a smaller fluence of CW blue light. Ambient light activated ALA-treated skin.


CONCLUSIONS
Both IPL and PDL are capable of activation of PDT but produce dramatically less PDT reaction than the standard CW blue-light broadband source. Physicians desiring a robust PDT response might select CW sources over pulsed sources. Ambient light may activate a PDT reaction.
Strasswimmer
John
J
Wellman Center for Photomedicine, Massachusetts General Hospital, & Department of Dermatology, Harvard Medical School, Boston, Massachusetts, USA.
Grande
Donald J
DJ
D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D001132:Arm; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D053685:Laser Therapy; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*
D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid