Comparative Epidemiology and Pathogenic Factors for Nonmelanoma Skin Cancer in Organ Transplant Patients

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Abstract
Organ transplantation has been performed for almost 40 years with steadily increasing success regarding long-time survival of the graft as well as quality of life for the patient. An increase of skin cancers as a consequence of the lowered cellular immune response seems to parallel the overall increased survival rate of organ transplant recipients. Against the background of chronic immunosuppression, known risk factors like the amount of sun exposure before and after transplantation and oncogenic viruses as well as the genetic background and place of residence (latitude) are strongly related with the increased skin cancer incidence. The goal of this review is to compare the epidemiologic prevalence of nonmelanoma skin cancer between various geographic locations and to highlight pathogenesis factors. This study was based on a review of the current literature. The increasing incidence of nonmelanoma skin cancer paralleling a prolonged survival of patients after organ transplantation represents a significant reason for morbidity and long-term mortality in organ transplant recipients worldwide. The incidence of nonmelanoma skin cancer in liver, kidney, and heart transplant recipients varies from 1.5% to 22%, 2% to 24%, and 6% to 34%, respectively, within 5 years of transplantation depending on geographic location and other pathogenesis factors. Ultraviolet radiation (UVR) as well as immunosuppressant therapy are crucial risk factors regarding the induction and progression of skin cancer. UVR is related to the induction of DNA damage as well as interference with Langerhans cell antigen presentation and a TH1-TH2 shift induced via release of IL-10. Whereas the overall duration of immunosuppression and the accumulative dosage applied are relevant measures in the pathogenesis of an increased tumor risk, individual differences between specific immunosuppressive agents are more difficult to assess. Multiple international studies assess risk factors and pathophysiology of skin cancer in organ transplant patients, with variable results in the literature. Large multicenter studies with thorough multivariant analysis may provide useful information for center-independent analysis of pathogenesis factors for transplant-related skin cancer.