Clearance of a Thick Invasive Squamous Cell Carcinoma After Multiple Treatments with Topical Photodynamic Therapy

Objective: Tumor depth is the limiting factor for topical photodynamic therapy (PDT) treating cutaneous invasive squamous cell carcinoma (SCC). The thickness of <2-3 mm below the epidermis is the currently recommended effective response depth in nonmelanoma skin cancers. We report an unusual outgrowing SCC with a tumor depth of 5.5 mm, which was successfully treated with PDT. Methods: Topical 20% (wt/wt) 5-aminolaevulinic acid emulsion was applied for 6 h before irradiation with 633-nm red light. The lesion was irradiated 7 times, 1 week apart, at a total dose of 791 J/cm(2). Results: Twelve months later, histologic and clinical examination showed a complete remission and no local or systemic metastases. No serious side effects occurred, and the cosmetic outcome was excellent. Conclusion: PDT may offer a noninvasive, well-tolerated, and effective therapy for inoperable low-risk SCC with an outgrowing pattern. It suggests that tumor depth is not an absolute predictor, but only a suggested reference.