Objectives: This study analyzed clinical characteristics of renal transplant recipients who developed malignancy with immunosuppression after transplantation by applying a competing risk analysis to reduce the effects of competing events.
Methods: All patients who underwent renal transplantation at our institution from 1973 to 2017 were included in this analysis. All data were collected from patient medical records and retrospectively analyzed. The cumulative incidence of malignancy before allograft loss and its risk factors were calculated by a competing risk analysis, the Gray test, and the Fine-Gray proportional hazard model.
Results: Of the 596 recipients, 78 developed malignancies. The mean age at transplantation was 38.5 ± 13.1 years. The median time from transplantation to the initial malignancy was 147.0 (5.2-407.3) months. The most common initial malignancy was skin cancer (21.8%), followed by posttransplant lymphoproliferative disease (14.1%). The cumulative incidence of malignancy at 20 years was 16.2% according to a competing risk analysis, whereas the conventional Kaplan-Meier method estimated the cumulative incidence at 20 years to be 25.6%. Increasing age at transplantation was significantly associated with the incidence of malignancy (P = .0091). Overall 10-year survival rates of recipients with and without malignancy were 81.7% and 88.5%, respectively (P < .001).
Conclusions: Results of time-to-event analysis must be interpreted with caution in situations with competing events when estimating the cumulative incidence of malignancy with immunosuppression after renal transplantation. Renal transplant recipients with increasing age should be more carefully monitored as a high-risk population for developing malignancies.
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