Photodynamic therapy for cutaneous squamous cell carcinoma in situ: impact of anatomic location, tumor diameter and incubation time on effectiveness

Background Photodynamic therapy (PDT) has been reported as a treatment for cutaneous squamous cell carcinoma in situ (SCCis) but there is limited data on the effectiveness of PDT with aminolevulinic acid (ALA-PDT). Objective To review the outcomes of SCCis treated with ALA-PDT and examine factors associated with response. Methods Retrospective review identified 58 patients with 68 primary SCCis lesions treated with ALA-PDT and blue light illumination. Patient demographics, lesion features, treatment details, clinical response, and subsequent recurrence were extracted from medical record review. Results Upon completion of PDT, the initial complete response rate was 77.9% and was not associated with the number of PDT treatments. On multivariate analysis, the factors associated with response were location on the face, tumor diameter <2 centimeters, and longer ALA incubation time. Lesions treated with a maximum incubation time of