234.12: Long-term Pancreas Graft Function – What Can We Expect in the Future?

Abstract

Background and Study Purpose: Outcome of recent pancreas transplants has improved significantly. Most advances are noted in the first year post-transplant. It is unknown if these improvements in short-term-outcome translate to improved long-term outcome. Assessment of long-term outcome depends on length of follow-up time. For transplants performed between 2008 and 2017 the actual follow-up time is not long enough to estimate long-term outcome. A mathematical model is needed to predict and verify long-term graft function. Methods: Between 1998 and 2017, 21,418 primary deceased donor pancreas transplants (77% SPK, 15% PAK, 8% PTA) in diabetic patients were reported to UNOS/IPTR with follow-up times depending on the year of transplant. Pancreas graft function was defined as insulin-independence and kidney graft function as being dialysis free. Dying with a functioning graft or partial graft function were defined as graft failures. Multivariate Cox regression models for pancreas and kidney graft function adjusted for donor, recipient and transplant factors were developed to functionally describe graft survival during different time periods. The model is based on the first 5 years post-transplant for the years 1998-2012 and the first 3 years for 2013-17 (due to shorter follow-up). Additional models were assessed for transplants which were functioning at 1-year post-transplant. Depending on the time period, half-lives then were estimated. The models were verified for the time periods 1998-02 and 2003-07, for which actual long-term results were available. Results: Table 1 shows the observed (1998-2007) or estimated (2008-2017) half-lives for the analyzed time period. The differences between observed and estimated half-life for transplants performed between 1998 and 2007 were actually small (2-5 months) so that we can assume that the estimates for the years 2008 to 2017 are reliable estimates. The models show that increased long-term graft function can be expected. Half-life for SPK performed in 2013-17 reached now 17 years for both organs and increases to more than 18 years for transplants that were functioning at 1 year post-transplant. The improved outcomes in PAK showed a doubling in half-life between 1998-02 and 2013-17. This improvement was greatest for grafts that had reached the 1-year time mark as functioning graft. The half-life of PTA also improved over time but did not reach the results of SPK. When a PTA graft is functioning at the 1-year mark, 50% of patients will still have graft function at 8 years post-transplant. Conclusions: These statistical models not only confirm improvements in long-term pancreas and pancreas/kidney transplantation but also show the expected duration of average graft function in the most recent eras. The models underline the importance of function throughout the first year post-transplant and its impact on long-term graft function.