Tumor Thickness Predicts Long-Term Complete Response of Facial Basal Cell Carcinomas in Asian Skin Types IV/V Treated with Methyl Aminolaevulinate Photodynamic Therapy

Abstract

Basal cell carcinoma (BCC) responds well to topical photodynamic therapy (PDT), with high clearance rates of 72-100%, although the therapy showed limited effectiveness for lesions > 2 mm thick. Tumor thickness is thought to be associated with therapeutic response. The purpose of this study was to investigate the efficacy, safety, and response depth of methyl aminolaevulinate (MAL) PDT for BCC. After application of MAL emulsion, each lesion was irradiated with 633-nm red light (total dose: 339 J/cm(2)). Complete response (CR) rates were assessed by histological examination at 6, 12, and 24 months. Forty-seven patients (95 lesions) with skin type IV/V were enrolled. Overall CR rate at 24 months was 75.8%. Superficial BCC was more responsive than other subtypes. Tumor thickness beyond subtype was significantly associated with CR rate. Three response depths are proposed: absolute CR (<1.3 mm), relative response (1.3 -1.8 mm) and no response (>1.8 mm). Although the recurrence rate (24%) is higher than with conventional surgical excision, 90.3% of patients were satisfied with the cosmetic outcome. MAL-PDT offers a noninvasive effective treatment; however, it is not the first option for most BCCs, except inoperable cases. The tumor thickness, independent of subtype, is predictive of PDT response.