Noninvasive fluorescence monitoring of protoporphyrin IX production and clinical outcomes in actinic keratoses following short-contact application of 5-aminolevulinate.
Topical 5-aminolevulinic acid (ALA) is widely used in photodynamic therapy (PDT) of actinic keratoses (AK), a type of premalignant skin lesion. However, the optimal time between ALA application and exposure to light has not been carefully investigated. Our objective is to study the kinetics of protoporphyrin IX (PpIX) accumulation in AK after short contact ALA and relate this to erythemal responses. Using a noninvasive dosimeter, PpIX fluorescence measurements (5 replicates) were taken at 20-min intervals for 2 h following ALA application, in 63 AK in 20 patients. Data were analyzed for maximal fluorescent signal obtained, kinetic slope, and changes in erythema. Our results show that PpIX accumulation was linear over time, becoming statistically higher than background in 48% of all lesions by 20 min, 92% of lesions by 1 h, and 100% of lesions by 2 h. PpIX accumulation was roughly correlated with changes in lesional erythema post-PDT. We conclude that significant amounts of PpIX are produced in all AK lesions by 2 h. The linear kinetics of accumulation suggest that shorter ALA application times may be efficacious in many patients. Noninvasive fluorescence monitoring of PpIX may be useful to delineate areas of high PpIX accumulation within precancerous areas of the skin.
Cleveland Clinic, Department of Dermatology, Dermatology and Plastic Surgery Institute, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA.
Christine B
CB
Warren
Sara
S
Lohser
Lauren C
LC
Wene
Brian W
BW
Pogue
Philip L
PL
Bailin
Edward V
EV
Maytin
D000287:Administration, Topical; D000368:Aged; D000622:Aminolevulinic Acid / Q000008:administration & dosage*; D004890:Erythema / Q000209:etiology / Q000473:pathology; D005260:Female; D005453:Fluorescence; D006801:Humans; D055623:Keratosis, Actinic / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D038761:Photobleaching; D010778:Photochemotherapy / Q000379:methods*; D011524:Protoporphyrins / Q000096:biosynthesis*; D016896:Treatment Outcome
D011524:Protoporphyrins; D000622:Aminolevulinic Acid; C028025:protoporphyrin IX