Islet Transplantation vs. Standard of Care for Type 1 Diabetes Complicated by Severe Hypoglycemia from the Collaborative Islet Transplant Registry (CITR) and the T1D Exchange (T1DX) Registry

Objective Islet transplantation is recently FDA-approved for adults with type 1 diabetes complicated by recurrent severe hypoglycemia events (SHE). We sought to understand the long-term benefit for glycemic control and risk of immunosuppression to kidney function associated with islet transplantation compared to ongoing standard-of-care. Research Design and Methods We performed a case-control analysis of prospectively collected data from patients in the Collaborative Islet Transplant Registry (CITR) with at least one SHE in the year (2000-2014) prior to transplant (cases) and compared them to patients in the T1D Exchange (T1DX) Registry with at least one SHE in the year (2010-2012) prior to enrollment (controls), with both cohorts followed over 5-years. SHEs were restricted to those resulting in seizure or loss-of-consciousness. Results Cases from CITR (n=71) compared to controls from T1DX (n=213) more often achieved the primary outcome of HbA1c <7.0% and absence of SHE (71–80 vs. 21–33% over 5-years; P <0.001), and the outcome of HbA1c ≤6.5% and absence of SHE (60–75% vs. 10–20%; P <0.001) while requiring significantly less insulin (majority in CITR insulin-independent). Kidney function, measured by estimated glomerular filtration rate, declined from baseline to a greater extent in CITR than in T1DX (-8.8 to -20 vs. -1.3 to -6.5 mL·min-1·1.73 m-2 over 5-years; P <0.001). Conclusions Islet transplantation for adults with type 1 diabetes complicated by SHE results in near-normal glycemic control in the absence of SHE more often than that observed with standard-of-care, but at the cost of greater reduction in kidney function.