Photodynamic Treatment for Precancerous Disease

Song, Ki Hoon; Lee, Chan Woo; Kim, Ki Ho

Abstract

BACKGROUND
Photodynamic therapy(PDT) is a treatment modality using a photosensitizer, light and oxygen to cause photochemically induced selective cell death. Topical PDT is an effective therapy for nonmalignant skin disease as well as various skin conditions. OBJECTIVE: The purpose of this study is to evaluate the effectiveness of PDT in the treatment of precancerous disease, and to evaluate the serial histopathologic findings after PDT. METHOD: PDT using 5-aminolaevulinic acid(ALA) was performed in 6 patients who had been diagnosed with extramammary Paget's disease, actinic cheilitis, actinic keratosis, Bowen's disease and arsenic keratosis. Histopathologic changes after PDT were evaluated by serial biopsy at pre-PDT and 2, 24, 48 hours, 7days post-PDT. TUNEL staining for detecting apoptotic cells was also performed. Light was administered at a wavelength of 600~800nm. The light intensity was 120mW/cm2 and the light dose ranged from 144J/cm2 to 216J/cm2. RESULT: Five patients showed a complete response at 1 month after the PDT and continued to show a complete response over six months. One patient showed a partial response and surgical intervention including laser ablation or conventional surgical excision has been needed. Early histopathologic changes after PDT were epidermal necrosis, band like dermal infiltration of inflammatory cells and thrombi formation in venules. At seven days after PDT, there was significant disappearance of abnormal cells in epidermis. Apoptotic cells were detected at 2, 24 hours post-PDT specimen and decreased from 48 hours post-PDT. CONCLUSION: PDT using 5-ALA is an effective and useful treatment modality for various precancerous skin tumors.