Photodynamic diagnosis of tumor margins using methyl aminolevulinate before Mohs micrographic surgery

Photodynamic therapy is an efficacious treatment modality for actinic keratoses and for superficial basal cell carcinoma (BCC) and squamous cell carcinoma. Only two prior case reports in the literature have used fluorescent diagnosis, with aminolevulinic acid, to define tumor margins.

Twenty patients with BCCs of the head, neck, and upper extremities were enrolled in this prospective trial. Methyl aminolevulinate (MAL) (Metvixia, Galderma Laboratories, LP, Fort Worth, TX) was applied overnight (mean of 13.3 hours) before fluorescence measurements of tumor size using a clinical Wood lamp examination.

A total of 5 (25.0%) superficial and 15 (75.0%) nodular BCCs were included in this trial. The mean tumor sizes were 263.0 mm(2) (post-Mohs micrographic surgery [MMS] defect), 239.1 mm(2) (fluorescent examination of MAL under Wood lamp), and 65.8 mm(2) (clinical size). Using interclass correlation coefficients, a high degree of consistency and absolute agreement between post-MMS defect size and fluorescent examination size was identified (interclass correlation coefficient .962). This correlation was significantly higher than that between post-MMS defect size and clinical examination (.703) and that between fluorescent and clinical examination (.651).

Although this study demonstrates the clinical feasibility of using MAL in conjunction with a Wood lamp examination to delineate tumor margins before MMS for superficial and nodular BCCs, future large-scale studies are needed.

The use of topical MAL as a photosensitizer in conjunction with a Wood lamp examination is a simple and inexpensive investigation that can be used before MMS to delineate the margins of ill-defined tumors.