Kidney transplantation is the gold standard treatment for end-stage kidney disease, significantly improving survival and quality of life. However, post-transplant malignancies (PTMs) remain a major concern, contributing to increased morbidity and mortality. This study investigates the incidence, characteristics, risk factors, and survival outcomes of PTMs among kidney transplant recipients at a single center in Taiwan over a 30-year period.

A retrospective cohort study was conducted on 1,808 patients who underwent kidney transplantation at Taichung Veterans General Hospital between 2002 and 2022. Exclusion criteria included pre-transplant cancer history, early PTM diagnosis (<3 months), and incomplete data. The final cohort consisted of 1,735 patients, including 203 diagnosed with PTM. Patient demographics, cancer types, survival outcomes, and immunosuppressive therapy associations were analyzed. Subgroup analyses focused on FK506 (Tacrolimus) levels and immunosuppressive drug use. Statistical significance was set at p ≤ 0.05.

The incidence of PTM was 11.23%. Bladder cancer (15.76%), upper tract urothelial carcinoma (14.29%), and liver cancer (12.32%) were the most common PTMs. The median time to PTM diagnosis was 8 years. Older age at transplantation was a significant risk factor (median age 52 years for PTM vs. 46 years for non-PTM, p < 0.001). PTM patients had a higher mortality rate (46.31%) compared to non-PTM patients. FK506 levels were lower in PTM patients (p < 0.05), with significantly higher levels before PTM diagnosis compared to post-diagnosis (p = 0.007). The use of more than five types of immunosuppressive drugs increased PTM risk significantly (p < 0.001).

PTMs are a significant burden among kidney transplant recipients, with older age and cumulative immunosuppressive burden identified as key risk factors. Tailored surveillance strategies and personalized immunosuppressive protocols are essential to mitigate PTM risk. Early cancer screening within the first five years post-transplant and further research on optimizing immunosuppressive regimens are recommended to improve patient outcomes.