Has the gap between pancreas and islet transplantation closed?

Both pancreas and islet transplantations are therapeutic options for complicated type 1 diabetes. Until recent years, outcomes of islet transplantation have been significantly inferior to those of whole pancreas. Islet transplantation is primarily performed alone in patients with severe hypoglycemia, and recent registry reports have suggested that results of islet transplantation alone in this indication may be about to match those of pancreas transplant alone in insulin independence. Figures of 50% insulin independence at 5 years for either procedure have been cited. In this article, we address the question whether islet transplantation has indeed bridged the gap with whole pancreas. Looking at the evidence to answer this question, we propose that although pancreas may still be more efficient in taking recipients off insulin than islets, there are in fact numerous "gaps" separating both procedures that must be taken into the equation. These "gaps" relate to organ utilization, organ allocation, indication for transplantation, and morbidity. In-depth analysis reveals that islet transplantation, in fact, has an edge on whole pancreas in some of these aspects. Accordingly, attempts should be made to bridge these gaps from both sides to achieve the same level of success with either procedure. More realistically, it is likely that some of these gaps will remain and that both procedures will coexist and complement each other, to ensure that β cell replacement can be successfully implemented in the greatest possible number of patients with type 1 diabetes.