Photodynamic therapy and pain: A systematic review

Photodynamic therapy (PDT) is an effective treatment for actinic keratoses and early skin cancers, and the only office procedure to control field cancerization. Procedure-associated pain limits widespread PDT use and by early termination of treatment can decrease overall therapeutic efficacy. Here we review and assess reported interventions on PDT-associated pain, in order to identify the most promising methods to manage treatment-associated pain and identify focus for future studies. Literature search was performed using MEDLINE, EMBASE, and the Cochrane Library by two independent reviewers to select publications that assessed and compared pain quantitatively during PDT treatment for actinic keratoses, basal cell carcinomas, and/or in situ squamous cell carcinomas. A total of 48 studies reporting on pain during PDT were identified and were comprised of two main categories of interventions: pain-controlling therapies and PDT parameter (photosensitizer or photo-irradiation) adjustments. Of these interventions: nerve block, subcutaneous infiltration anesthesia, cold analgesia, and transcutaneous electrical nerve stimulation, but not topical anesthetic gels, were associated with less PDT-related pain; 5-aminolevulinic acid (ALA) tended to be more painful than methyl-5-aminolevulinate (MAL); daylight PDT was less painful than conventional PDT; and lower irradiance delivery produced lower pain scores in general. There is no single crystalized protocol for management of PDT-related pain. Evidence suggests that continuous activation of low levels of PpIX with methods using lower irradiance and possibly shorter incubation times are associated with decreased pain without loss of PDT efficacy. Protocols to reduce pain should be standardized and large controlled trials are needed.