[Carcinogenic risks of phototherapy and photochemotherapy].

The data in the literature regarding the carcinogenic risks involved in both UVB phototherapy and 8-methoxypsoralen plus UVA photochemotherapy are discussed. Both modes of treatment can be mutagenic and can induce immunosuppression. Which of the two factors (the initiator or the promoter effect) is more responsible for the carcinogenic risks involved in phototherapy or photochemotherapy is a subject of much controversy. In addition to discussing the theoretical background, the present article also takes into consideration the long-term clinical studies that have been performed. Practical guidelines are given on how to apply phototherapy and photochemotherapy as safely as possible.