Cancer Incidence and Outcomes After Kidney Transplantation in Balkan Nephropathy Patients

Background: Balkan nephropathy (BEN), caused by chronic dietary exposure to aristolochic acid (AA), is a tubulointerstitial kidney disease strongly associated with upper-tract urothelial carcinoma (UTUC). Patient and graft survival, the cumulative incidence and timing of post-transplant UTUC, and the burden of non-urothelial malignancy after kidney transplantation remain poorly defined. Methods: We retrospectively analyzed all patients with BEN as the primary cause of end-stage kidney disease transplanted at University Hospital Center Zagreb between October 1973 and December 2023. Outcomes included patient and graft survival, the incidence and timing of post-transplant UTUC, and burden of non-urothelial malignancies. Results: Of 2282 kidney transplants performed in the study period, 44 (2%) were in patients with BEN. The median age at transplantation was 56 years, and the median dialysis vintage was 3.7 years. After 10 years (median) of follow up, among 34 patients with adequate follow-up, 16 (47%) developed a de novo malignancy: eight (24%) UTUC, one renal cell carcinoma, four other solid tumors, and three hematological. UTUC was diagnosed between 6 months and 15 years post-transplant (median 7 years); five of eight patients died within one year of diagnosis. Five- and ten-year patient survival rates were 82% and 54.5%. Conclusions: Kidney transplantation in patients with BEN carries a lifelong cancer risk dominated by UTUC. Prophylactic bilateral nephroureterectomy should be the default management strategy when feasible, with lifelong surveillance extending beyond the urothelium.