Whether kidney transplant recipients who were treated for a malignant tumor prior to transplantation are at an increased risk of developing a tumor post transplantation has not been adequately quantified and characterized.Methods
We studied more than 270 000 patients on whom pre and posttransplant malignancy data were reported to the Collaborative Transplant Study. More than 4000 of these patients were treated for pretransplant malignancy. The posttransplant tumor incidence in these patients was compared to that in recipients without a pretransplant tumor. Cox regression considering multiple confounders was applied.Results
Significant increases in posttransplant tumor incidence with HR ranging from 2.10 to 5.47 (all P<0.001) were observed for tumors in the site-specific pretransplant locations, suggesting tumor recurrences. There were also significantly increased de novo tumors in new locations with HR ranging from 1.28 to 1.89. Pretransplant basal cell carcinoma of the skin and male genital cancer were associated with significantly increased death-censored graft survival, suggesting impaired immune responsiveness against transplanted kidneys. Time interval from pretransplant tumor occurrence to transplantation and posttransplant mTOR inhibitor treatment were not found to be of significant relevance in this study.Conclusions
Patients who experienced a pretransplant tumor are at significant risk of tumor recurrence, regardless of the length of interval between tumor treatment and transplantation. There is also some increased risk for de novo tumors, suggesting impaired immune surveillance. Impaired tumor immunity appears to extend to a lower rate of transplant rejection because patients with pretransplant tumors tended to show improved death-censored graft survival.