Malignancy concerns with psoriasis treatments using phototherapy, methotrexate, cyclosporin, and biologics: facts and controversies.

Cancer is one of the several comorbidities that have been linked with psoriasis. Not surprisingly, tumors associated with well-documented risk factors for the dermatosis, such as smoking and obesity, have been found with increased incidence in psoriatic patients. They include lung, kidney, and colon cancers. For unknown reasons, the risk of lymphoma is also increased in psoriatic patients. Despite several difficulties with documenting risks, some systemic treatments for psoriasis have been linked with an increased risk of selected cancers. The best-documented association is nonmelanoma skin cancer with psoralen plus ultraviolet A therapy and cyclosporin. More recently, an increased risk of cancer has been a concern with newly introduced biologic agents. The documentation of such a purported increased risk requires long-term follow-up of treated patients.