title: Comparison of protoporphyrin IX accumulation and destruction during methylaminolevulinate photodynamic therapy of skin tumours located at acral and nonacral sites.
abstract: BACKGROUND
  Topical photodynamic therapy (PDT) is successful in the treatment of nonmelanoma skin cancers and associated precancers, but efficacy is significantly reduced in actinic keratosis lesions not located on the face or scalp.
  
  
  OBJECTIVE
  To compare the changes in protoporphyrin IX (PpIX) fluorescence in lesions undergoing routine methylaminolevulinate (MAL) PDT and the clinical outcome observed 3 months after treatment in lesions located at acral and nonacral sites.
  
  
  METHODS
  This study was a noninterventional, nonrandomized, observational study, which monitored changes in PpIX fluorescence in 200 lesions during standard dermatological MAL-PDT. These data were subsequently analysed in terms of lesions located at acral and nonacral sites.
  
  
  RESULTS
  Clinical clearance was significantly reduced (P < 0·01) in acral skin lesions when compared with lesions located at nonacral sites. The accumulation and destruction of PpIX fluorescence was significantly reduced in these acral lesions (P < 0·05 and P < 0·001, respectively). Specifically, lesion location at acral sites significantly reduced changes in PpIX fluorescence in actinic keratosis lesions during MAL-PDT (P < 0·01 and P < 0·05).
  
  
  CONCLUSIONS
  These data suggest that reduced PpIX accumulation and the subsequent reduction in PpIX photobleaching within acral lesions result in the reduced responsiveness of these lesions to MAL-PDT. Future work should therefore aim to improve photosensitizer accumulation/photobleaching within lesions located at acral sites.
authors.affiliation: Clinical Photobiology, European Centre of Environment and Human Health, Peninsula Medical School, University of Exeter, Royal Cornwall Hospital, Treliske, Truro, Cornwall, UK.
authors.forename: J S
authors.initials: JS
authors.lastname: Tyrrell
authors.forename: C
authors.initials: C
authors.lastname: Morton
authors.forename: S M
authors.initials: SM
authors.lastname: Campbell
authors.forename: A
authors.initials: A
authors.lastname: Curnow
mesh_terms: D000328:Adult; D000368:Aged; D000622:Aminolevulinic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000704:Analysis of Variance; D005121:Extremities; D005148:Facial Dermatoses / Q000188:drug therapy; D005260:Female; D005453:Fluorescence; D006801:Humans; D055623:Keratosis, Actinic / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D011230:Precancerous Conditions / Q000188:drug therapy; D011524:Protoporphyrins / Q000378:metabolism*; D012536:Scalp Dermatoses / Q000188:drug therapy; D012878:Skin Neoplasms / Q000188:drug therapy* / Q000378:metabolism
chemical_list: D017319:Photosensitizing Agents; D011524:Protoporphyrins; C475457:methyl 5-aminolevulinate; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX