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

Background: 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. Objective: The purpose of this study was to investigate the efficacy, safety, and response depth of methyl aminolaevulinate (MAL) PDT for BCC. Methods: After application of MAL emulsion, each lesion was irradiated with 633-nm red light (total dose: 339 J/cm²). Complete response (CR) rates were assessed by histological examination at 6, 12, and 24 months. Results: 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. Conclusions: 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.