Response of Bowen Disease to ALA-PDT Using a Single and a 2-Fold Illumination Scheme

T he use of topical 5-aminolevulinic acid–photodynamic therapy (ALA-PDT) for the treatment ofBowendisease(squamouscell carcinomainsitu) is gaining acceptance. However, there is limited evidence for themostappropriate treatmentregimen,andclinical follow-up remains limited. The treatment of choice for Bowen disease is surgery. Five-year response rates have shown a recurrence rate of 19.0% after conventional surgery and 6.3% after Mohs micrographic surgery. In a comparison of ALA-PDT and cryotherapy, results significantly favored ALA-PDT. In a comparative study of ALA-PDT vs topical fluouracil, recurrence rates at 12 months were 7% and 27%, respectively. In a review of 11 PDT studies using broadly similar protocols, response rates of 90% to 100% were found after 1 to 3 treatment sessions, and an average recurrence rate of 12% was calculated. Importantly, however, follow-up periods varied widely (3-36 months), and therapy was often repeated. Our research group has investigated the role of light fractionation in the response of tissues to ALA-PDT in animal and clinical studies. In a randomized comparative study of the response of superficial basal cell carcinoma (sBCC) to ALA-PDT, our group showed a significantly higher complete response rate at 1 year (n=476) (P=.002) using a 2-fold illumination scheme (20 80 J/cm) with a 2-hour dark interval compared with a single illumination (75 J/cm).