A prospective study of pain control by a 2-step irradiance schedule during topical photodynamic therapy of nonmelanoma skin cancer.

Abstract

Topical photodynamic therapy (PDT) for selected nonmelanoma skin cancer using 5-aminolevulinic acid (ALA) or methyl aminolevulinate (MAL) has yielded high long-term complete response rates with very good cosmesis. Pain during light activation of the photosensitizer can be a serious adverse event. A 2-step irradiance protocol has previously been shown to minimize ALA-PDT pain. To determine the irradiance-dependent pain threshold for MAL-PDT, to adapt the 2-step protocol to a light-emitting diode (LED) light source, and assess clinical response. In this prospective study, 25 superficial basal cell carcinoma (sBCC) received an initial irradiance by laser at 40 or 50 mW/cm², or LED at 35 mW/cm² followed by an irradiance at 70 mW/cm² for a total of 75 J/cm². Pain levels were recorded for both irradiance steps. Efficacy was assessed at 6, 12, or 24 months. Pain was mild in the 40/70 mW/cm² laser cohort. Three instances of irradiance-limiting pain occurred at 50/70 mW/cm². Pain was minimal in the 35/70 mW/cm² LED cohort. Clinical response rates were 80% in the 50/70 mW/cm² laser cohort and 90% in the 35/70 mW/cm² LED cohort. Topical PDT can be effectively delivered to sBCC with minimal treatment-related pain by a 2-step irradiance protocol.