Factors affecting the choice of a ceiling on the number of exposures with TL01 ultraviolet B phototherapy

Sir, Recommending the maximum number of lifetime exposures in order to limit the risk of phototherapy‐induced skin cancer is best achieved from recorded incidence data as a consequence of the therapy. These data are not yet available and it will be a decade or more before we can expect them. In the meantime, the most defensible approach is to incorporate mathematical models of skin cancer incidence with estimates of human exposure to both sunlight and therapeutic ultraviolet (UV) B in order to arrive at risk estimates. Risk analysis of human skin cancer. Estimates of the risk of inducing skin cancer from exposure to UV radiation demand knowledge of dose–response relationships and the relative effectiveness of different wavelengths (known as an action spectrum) in inducing skin cancer. Data on dose–response relationships and action spectra are available to some extent to allow quantitative estimates of the effects of TL01 phototherapy on nonmelanoma skin cancer (NMSC) incidence, but remain unknown for malignant melanoma.