Objectives. This report summarizes the experience in the Nordic countries with de novo cancer complicatingrenal transplantation and the prospects of a new Nordic EU-SPONSORED study (EURO-CA T) covering all kinds of organ transplantations. Methods. Epidemiological studies are performed using standard methods of cohort analysis. The expected numbers of cancer cases in each stratum are calculated by applying the stratum- and site-specific cancer incidence rate of the national population to the appropriate number of person-years at risk. The observed/expected ratio is taken as the relative risk (standardized incidence ratio, SIR). Differences in SiRs between subcohorts are tested by evaluating the rate ratio. Laboratory methods include immunopathological, virus serological, cytokine and tissue type analyses. Treatment includes discontinuation of immunosuppression and long-term high dose aciclovir. Results. In our most recent analyses an incidence 3 - 5 times higher than that of the general population has been found, including most types of tumors, however with an uneven pattern with emphasis on lip- cervical-, vulvar-, urological-, skin cancers and Iymphoprolipherative disorders (PTLD). Most tumors occur early (incl. PTLD) after transplantation, tumors of the skin however later and with an increase with time. In our present analysis we follow alltypes of organ transplantation, up to the most recent date, to consider the many new immunosuppressive agents for their risk of inducingcancer. Laboratoryanalyseshave pointed to IL-IOas a possiblecofactor in the development of EBV-inducedPTLD.Treatment with aciclovirand discontinuation of immunosuppression may in some cases lead to recovery from the malignancy, sometimes even without harming the graft function.

Keywords: cancer, Transplantation, Immunosuppression