Comparison of steroid avoidance in tacrolimus/mycophenolate mofetil and tacrolimus/sirolimus combination in kidney transplantation monitored by surveillance biopsy

Background. Chronic steroid therapy in kidney transplantation has myriad side effects and steroid avoidance has become feasible. This prospective study compared the safety and efficacy of steroid avoidance in tacrolimus (TAC)/ mycophenolate mofetil (MMF) and TAC/sirolimus (SRL) combinations in kidney transplantation. Methods. In all, 150 kidney recipients were analyzed: 75 each in TAC/MMF and TAC/SRL groups. The primary endpoint was acute rejection. Surveillance biopsies were completed to analyze subclinical acute rejection (SCAR) and chronic allograft nephropathy (CAN). Acute rejection and SCAR were treated by methylprednisolone. Two-year patient and graft survival, renal function, and adverse effects were monitored. Results. Acute rejection was seen in 12% of TAC/MMF and 8% of TAC/SRL patients. Two-year actuarial patient survival was 95% and 97%, and graft survival 90% and 90% in TAC/MMF and TAC/SRL groups, respectively. Surveillance biopsy showed cumulative incidence of SCAR was 27% in TAC/MMF and 16% in TAC/SRL groups at 2 years (P=0.04). Overall, 33% of recipients in TAC/MMF and 20% in TAC/SRL received methylprednisolone for acute rejection/SCAR. Moderate/severe CAN was 1.0% in TAC/SRL group and 22% in TAC/MMF group(P=0.06). New-onset diabetes mellitus (NODM) was 4% each in both groups. All recipients remain free of maintenance steroid therapy. Conclusions. Steroid avoidance in tacrolimus-based immunosuppression with MMF or SRL provides equivalent 2-year patient and graft survival with a low incidence of acute rejection and NODM. SCAR and CAN are lower in TAC/SRL compared to TAC/MMF group. The impact of decreased SCAR and CAN in TAC/SRL group on longer-term graft survival and function is to be evaluated.