title: Temperature-modulated photodynamic therapy for the treatment of actinic keratosis on the extremities: a pilot study.
abstract: BACKGROUND
  The efficacy of photodynamic therapy (PDT) using topical 5-aminolevulinic acid (ALA) for the treatment of actinic keratosis (AKs) is lower on the distal extremities compared with the head and neck areas. The strong temperature dependence of porphyrin synthesis in biologic tissue suggests that heating skin during incubation may improve the efficacy of PDT, particularly in areas where biologic temperatures are naturally lower. The aim of this study was to evaluate the efficacy and tolerability of temperature-modulated PDT for the treatment of AKs on the extremities.
  
  
  METHODS
  In this IRB-approved, single-center study, the upper or lower extremities of 20 subjects were treated with 20% ALA under occlusion, followed by 10 J/cm, 417-nm blue light. One of the 2 extremities treated was heated during the 1-hour incubation. Outcome measures included lesion counts, tolerability, and global improvement at baseline, 1 week, and 2 and 6 months after treatment.
  
  
  RESULTS
  The median temperatures of the heated and control sides were 38.8°C and 29.4°C, respectively. The median clearance for the heated side was significantly greater than the control side at 2 and 6 months (p < .0001). Typical PDT side effects were greater on the heated side compared with the control yet were well tolerated by all subjects.
  
  
  CONCLUSIONS
  Warming the skin during incubation of ALA seems to improve the efficacy of PDT in the treatment of AKs on the extremities and is well tolerated when heat application is controlled within the limits of safety.
authors.affiliation: *Andrea Willey, MD, PMC, Surgical & Aesthetic Dermatology, Sacramento, California; †Department of Dermatology, University of California Davis, Sacramento, California; ‡Department of Dermatology, Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts; §Department of Dermatology, Harvard Medical School, Boston, Massachusetts.
authors.forename: Andrea
authors.initials: A
authors.lastname: Willey
authors.forename: R Rox
authors.initials: RR
authors.lastname: Anderson
authors.forename: Fernanda H
authors.initials: FH
authors.lastname: Sakamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000622:Aminolevulinic Acid / Q000627:therapeutic use*; D001768:Blister / Q000209:etiology; D002985:Clinical Protocols; D004890:Erythema / Q000209:etiology; D005121:Extremities; D005260:Female; D006801:Humans; D055623:Keratosis, Actinic / Q000188:drug therapy*; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000209:etiology; D010778:Photochemotherapy / Q000009:adverse effects / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D010865:Pilot Projects; D012881:Skin Temperature; D013696:Temperature; D016896:Treatment Outcome
chemical_list: D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid