The Efficacy of Photodynamic Diagnosis in Defining the Lateral Border Between a Tumor and a Tumor-Free Area During Mohs Micrographic Surgery

BACKGROUND Photodynamic diagnosis (PDD) is a preoperative procedure that simplifies Mohs micrographic surgery (MMS) by allowing more accurate demarcation of neoplastic lesions involving the skin. After topical application of aminolevulinic acid (ALA), protoporphyrin IX (PpIX) is selectively induced in neoplastic cells with a high tumor-to–surrounding tissue ratio and can be visualized after excitation using a Wood's lamp. OBJECTIVES To evaluate the efficacy of PpIX fluorescence images in accurately determining the boundaries of tumors during MMS. METHODS A retrospective evaluation of biopsy-proven basal cell carcinoma (BCC; n=163), squamous cell carcinoma (SCC; n=51), and Bowen's disease (n=8) in 222 patients treated with MMS was conducted. In the PDD group, 20% ALA ointment was applied 6 hours before the surgery, and then the boundaries were mapped based on the red fluorescence of the Wood's lamp in the operating room. Each of the PDD (n=142) and non-PDD (n=80) groups was surgically staged and compared. RESULTS The average number of stages was 1.59, with more in the PDD group (1.66) than the non-PDD group (1.44) (p=.05). The average number of stages was 1.77 in the PDD group and 1.50 in the non-PDD group (p=.06) for BCC, was 1.40 in the PDD group and 1.37 in the non-PDD group (p=.90) for SCC, and 1.25 in the PDD group and 1.00 in the non-PDD group (p=.36) for Bowen's disease. CONCLUSIONS In previous studies, the fluorescence of induced porphyrins was effective in detecting and delineating neoplastic skin areas, but, in the present study, PDD did not support surgical efficacy during MMS. The authors have indicated no significant interest with commercial supporters.