Photodynamic therapy with a 5-ALA patch does not increase the risk of conversion of actinic keratoses into squamous cell carcinoma: Results of a multicentre non-interventional study

Background: It is important to collect data about the risk of transformation of an actinic keratosis (AK) lesion into squamous cell carcinoma (SCC) after a single photodynamic therapy (PDT) with 5-ALA patch for a longer follow-up period under daily routine. Questions addressed: The purpose of this non-interventional study (NIS) was to collect data on the frequency of occurrence of SCCs in the treated area during an interval of 2 years after a single 5-ALA patch-PDT. Experimental design: This prospective observational case-only study included patients with mild AK lesions on the head and face treated with 5-ALA patch-PDT according to the Summary of Product Characteristics (SPC). Results: In 370 patients, the risk of transformation of their treated AK lesion into SCC was 0.073% with its exact 95% confidence interval using the Poisson distribution of [0.009%, 0.262%]. The rate of complete clinical clearance on lesion basis after 3 months was 84.3%. Conclusion: The efficacy and the safety results show no observation of an increased risk for conversion of an AK into a SCC 2 years after a single 5-ALA patch-PDT. Additionally, the high clinical complete remission rate under routine conditions is comparable to the rates observed in the approval trials.