In dermatology, photodynamic therapy (PDT) has been used primarily for treating malignant skin tumors and involves the sequential administration of photosensitizing drugs and light to patients. Aminolevulinic acid is a naturally occurring porphyrin precursor that can photosensitize cutaneous neoplasms for destruction by light when applied topically in pharmacologic doses. Exogenous topical aminolevulinic acid appears to be taken up preferentially by tumors and metabolized in situ to protoporphyrin IX, a photosensitive compound.1,2 Kennedy et al1,2 reported first on the use of topical aminolevulinic acid and red light to photosensitize skin tumors in patients. There has been limited longterm clinical follow-up data concerning patients treated with aminolevulinic acid and light, and there is also a lack of detailed histologic studies assessing microscopic tumor responses to therapy.
Subjects and Methods.
Five patients with one or more biopsy-proven and previously untreated basal cell or squamous cell (in situ or invasive) carcinomas measuring