Introduction: Patients with a pre-transplant (pre Tx) malignancy were reported to be at an increased risk of developing cancer after kidney transplantation. However, the preferred location of such malignancies was not addressed. Using the CTS database we analyzed the incidence and site of post-transplant (post Tx) malignancies that occurred in patients with different types of pre Tx cancer.
Materials and Methods: Recipients of first kidney-only transplantations performed between 1984 and 2015 were analyzed for 10-year cancer occurrence. Cancers diagnosed on the day of transplantation were excluded. Using multivariable Cox-regression, the hazard ratio (HR) of post Tx cancer was calculated for 3,948 patients with different types of pre Tx cancer as compared to 263,142 patients without pre Tx cancer (Table 1).
Results: The location and HR of post Tx cancer in patients with pre Tx genital, urinary, lymphoma or non-melanoma skin cancer (NMCS) are shown in Table 2. All other cancers were merged in the heterogeneous ‘other solid’ category. A strong tendency was observed for the occurrence of post Tx cancer at the pre Tx location. The highest evidence was observed with HR 5.63 for urinary tract cancer in patients with a pre Tx cancer at the same site (P<0.001).

Discussion: As shown in Table 2, several cancer sites appeared to be linked to each other, e.g. an increased risk of genital cancer was observed also in patients with a pre Tx cancer of the urinary tract (HR=1.69, P=0.015). A dissemination trend was observed in patients with pre Tx lymphomas; due to insufficient case numbers, statistical significance was reached only for the group combining all post Tx cancers without NMSC (HR=2.46, P<0.001).
Conclusion. Patients with a pre Tx cancer history should be checked regularly for the development of a malignancy after transplantation, especially at the site of the pre Tx cancer. In patients with pre Tx lymphoma, post Tx cancers at various locations are common.