Incidence of BK Is Higher in Recipients On Tacrolimus vs. Cyclosporine On Rapid Steroid Discontinuation Protocols.

Background: BK nephropathy is an important cause of kidney allograft failure. Yet, little data exists on the risks of individual immunosuppressive drugs, either with or without prednisone maintenance therapy. Routine monitoring for BK viremia (BKV) began (at our institution) in 2008. We studied incidence of BKV in recipients on a rapid discontinuation of prednisone (RDP) protocol including either CSA or FK (polyclonal Ab, CNI, MMF, and RDP). Multivariate analysis (MVA) was done to determine risk factors for BKV. Variables included in the analysis were: recipient race and gender, age>50, DD vs. LD, donor race and gender, dialysis prior the transplant, CNI (FK vs CSA) and incident of acute rejection. Results: Between 2008 and November, 2013, 415 recipients (FK =172; CSA = 287) were screened for BKV using BK PCR. Recipients demographics are shown in table 1: significant differences existed between groups in donor source (p=.04) and dialysis prior to tx (p=.02)Table: No Caption available.There were no difference between groups in patient or graft survival or in acute rejection rates. A total of 39 recipients (8.4%) developed BKV (TAC, 21; CSA, 18). Cumulative incidence at 5 years was 13.2 % in TAC and 7.6% in CSA (Figure). Kaplan-Meier BK free survival curves in recipients on FK+MMF (blue) and CSA+MMF (red).Figure: No Caption available.By MVA the only risk factor for BKV was maintenance FK vs. CSA (p=0.03; HR 1.96, CI 1.0-3.6). Of note, recipients on FK had significant higher MPA levels at 1 month posttxt (3.0±1.8 vs. 1.7± 1.5, p <0.0001); Addition of 1 month MPA levels >3 mcg/ml to the MVA model did not show significance. 5 years graft survival was 86% on CSA +MMF and 83% on FK+MMF (NS). Conclusion: Recs on RDS protocol receiving FK +MMF combination have higher risk for BK. Exposure to MMF is higher in recs on TAC, but did not show to be a significant risk factor in MVA.