Pancreas transplantation for diabetes mellitus: a guide to recipient selection and optimum immunosuppression

Between 1966 and 1997, over 10 000 pancreas transplants were performed worldwide, 88% of these being simultaneous kidney-pancreas transplantations (SKPTs). The overall 1-year patient survival rate exceeds 90%, and the graft survival (complete insulin independence) rate is 80%. SKPT should be regarded as the treatment of choice in carefully selected patients with type 1 (insulin-dependent; IDDM) diabetes mellitus and advanced nephropathy, because of its ability to offer superior glycaemic control and an improved quality of life. Studies have shown that the addition of a pancreas transplant does not appear to jeopardise either the patient or the kidney transplant, as many centres report either similar or improved survival rates after SKPT compared with kidney transplantation alone. Indications for solitary pancreas transplantation are based on the presence of early, well defined diabetic complications or glucose hyperlability with poor quality of life. Improvements in quality of life and possible prevention of further morbidity associated with diabetes makes pancreas transplantation an important therapeutic option for selected diabetic patients. According to registry data from the United Network for Organ Sharing (UNOS) Registry, rejection accounts for 32% of graft failures in the first year after pancreas transplantation. Most pancreas transplant centres employ quadruple drug immunosuppression with antilymphocyte induction with either a monoclonal or polyclonal agent. Maintenance immunosuppression involves triple therapy, consisting of a calcineurin inhibitor (cyclosporin or tacrolimus), corticosteroids and an antimetabolite (azathioprine or mycophenolate mofetil). Before 1995, nearly all pancreas transplant recipients were managed with the original formulation of cyclosporin ('Sandimmun'). In the past 2 years, tacrolimus-based therapy has been used in approximately 20% of cases and a new microemulsion formulation of cyclosporin ('Neoral') has replaced the original formulation in contemporary post-transplant immunosuppression. In addition, mycophenolate mofetil is replacing azathioprine as part of the standard immunosuppressive regimen after pancreas transplantation. At present, a number of centres are conducting various trials with new drug combinations including either cyclosporin microemulsion or tacrolimus in combination with corticosteroids and mycophenolate mofetil with or without antibody induction therapy. The current array of new immunosuppressive agents is providing more effective control of rejection and permitting solitary pancreas transplantation to become an accepted treatment option in diabetic patients without advanced complications. Immunosuppressive strategies will continue to evolve to achieve effective control of rejection while minimising 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.