Evaluation of the chemopreventative effects of ALA PDT in patients with multiple actinic keratoses and a history of skin cancer

Background: Actinic keratoses (AKs) are in situ epidermal tumors that may progress to invasive squamous cell carcinomas (SCCs). Aminolevulinic acid with photodynamic therapy (ALA PDT) is a field treatment for AK. Objective: To evaluate the time to development of new non-melanoma skin cancers (NMSC) within one year of ALA-PDT treatment in immunocompetent patients with AK and a history of skin cancer. Methods and Materials: One hundred forty anatomic sites in 114 patients were treated with topical ALA for a 1 to 3 hour incubation period followed by photodynamic therapy (PDT) with a blue light. All new NMSCs within the treatment areas were recorded over a 1-year observational period. Results: Eighty-three anatomic sites (59%) did not develop new skin cancers within 1 year. Additionally, 92%, 78%, and 64% of anatomic sites were free of new skin cancers at 3, 6, and 9 months after treatment was initiated. Although approximately 41% of patients treated on both the scalp and face developed new skin cancers within 1 year of treatment, the average time to develop skin cancer was longer for the face (7.09 months) than for the scalp (5.34 months). Conclusion: In patients with a history of NMSC and multiple AKs, ALA PDT may be a valuable option for the prevention and delay of new NMSCs.