Review of immunosuppressive usage in pancreas transplantation

Throughout 1997, nearly 10,000 pancreas transplants have been performed worldwide, with 88% being simultaneous kidney transplants (SKPT). The current 1 yr patient survival rate exceeds 90% and pancreas graft survival (complete insulin independence) rate exceeds 80% for SKPT, 70% for sequential pancreas after kidney transplant (PAKT), and 65% for pancreas transplant alone (PTA). According to registry data, rejection accounts for 32% of graft failures in the first year after pancreas transplantation. However, improvements are expected to continue with the evolution of treatment protocols. Most pancreas transplant centers employ quadruple drug immunosuppression with anti-lymphocyte induction with either a monoclonal or polyclonal antibody agent. In recent years, there has been an overall decline in the use of antibody induction therapy from 90% during the period 1987-1993 to 83% of pancreas transplants performed during 1994-1997. Maintenance immunosuppression is triple therapy consisting of a calcineurin inhibitor (cyclosporine or tacrolimus), corticosteroids, and an anti-metabolite (AZA or MMF). Prior to 1995, nearly all pancreas transplant recipients were managed with Sandimmune. In the last 2 yr, tacrolimus-based therapy has been used in approximately 20% of cases and a new microemulsion formulation of cyclosporine (Neoral) has replaced Sandimmune in contemporary post-transplant immunosuppression. In addition, MMF is replacing AZA as part of the standard immunosuppressive regimen after pancreas transplantation. At present, a number of centers are conducting various trials with new drug combinations including either Neoral or tacrolimus in combination with steroids and MMF with or without antibody induction therapy. From 1994 to 1997, the 1 yr rates of immunologic graft loss have decreased to 2% after SKPT, 9% after PAKT, and 16% after PTA. The current array of new immunosuppressive agents are providing more effective control of rejection and permitting solitary pancreas transplantation to become an accepted treatment option in diabetic patients without advanced complications. The apparent potency of new drug combinations has also resulted in a resurgence of interest in steroid withdrawal. Immunosuppressive strategies will continue to evolve in order to achieve effective control of rejection while minimizing injury to the allograft and risk to the patient. In addition, new regimens must not only address the issue of specific drug toxicities but also long-term economic, metabolic, and quality of life outcomes. Pancreas transplantation will remain an important alternative in the treatment of diabetic patients until other strategies are developed that can provide equal glycemic control with less immunosuppression and overall morbidity.