621 A novel painless ALA-PDT in the treatment of skin diseases

Abstract

Pain during conventional photodynamic therapy (C-PDT) is the main limiting adverse effect in its use in dermatology. During the course of C-PDT, most patients experience sensations of burning and tingling pain that vary in intensity. In some cases, patients have to stop the treatment because of unbearable pain. It is generally believed that C-PDT pain is mediated by free radicals generated by PpIX; ROS can either stimulate nerve endings directly or mediate pain through inflammatory by-products. Pain remains the top obstacle that prevents C-PDT application to all patients. Here, we modified C-PDT into a painless PDT treatment (Modified photodynamic therapy , M-PDT, also named novel painless ALA-PDT) by decreasing ALA incubation time and increasing light dose. Our study showed that pain in M-PDT group was significantly reduced in the treatment of actinic keratosis, acne, and condyloma acuminate. Even, in some cases the pain almost vanished. And M-PDT has better efficacy than C-PDT. Further investigation confirmed that M-PDT also inhibit tumor growth on cutaneous squamous cell carcinoma (SCC). Interestingly, compared with C-PDT, M-PDT induced more ROS which should stimulate nerve endings but not. We elucidated a mechanism that the low average amount of ROS may be the reason why M-PDT is painless. Our findings indicate that M-PDT have wide clinical value in skin disease.