1 Introduction

The postpandemic recovery seen in other organs has not occurred in pancreas transplantation due to a combination of factors. The proportion of patients with type 2 diabetes undergoing pancreas transplant decreased for the first time in the past few years, probably related to newer noninsulin therapies for diabetes, improvement in medical management of diabetes, decreased risk tolerance by centers and patients, broader sharing with an increase in cold ischemic time, and lack of widespread surgical expertise for pancreas procurement and transplant. Initiatives to identify and address some of these issues are underway by various bodies, including the Organ Procurement and Transplantation Network’s (OPTN) Pancreas Transplantation Committee, the American Society of Transplantation’s Kidney Pancreas Community of Practice, and the International Pancreas and Islet Transplant Association’s pancreas working group.

Meanwhile, outcomes after pancreas transplant continued to improve and in 2022 were probably the best they have ever been. Technical failures, immunologic loss, and short- and long-term graft and patient survival have all shown a positive trend. The definition of pancreas graft failure adopted in 2018 has helped set uniform criteria for failure, but these criteria will need refinement in the future as acknowledged at their implementation. In addition, the lack of data on recipient body weight and insulin dose poses a major issue. In particular, graft failure due to insulin dependence cannot be independently calculated from OPTN/Scientific Registry of Transplant Recipients (SRTR) data, because recipient body weight is not collected on transplant follow-up forms and transplant centers are allowed to report follow-up insulin dosage as missing, unknown, or not done.

The SRTR rolled out the new organ allocation simulator (OASIM) in 2022. The OPTN’s Kidney and Pancreas Transplantation Committees’ data requests for continuous distribution were simulated in fall 2022. After the report, the committees refined the request in March 2023 and a second simulation was run in summer 2023. This second round of modeling was more detailed and granular in nature. The scenarios modeled sought to explore different ratios of proximity efficiency to qualifying time while maintaining appropriately high access for candidates with high calculated panel reactive antibody (cPRA), pediatric candidates, and prior living donor candidates. At the time of this writing, the report is being reviewed by both Committees to decide on further action. The Pancreas Committee is in discussion for including a medical urgency attribute to the pancreas continuous distribution framework. A review-based medical urgency attribute will create a pathway for medically urgent pancreas patients and allow the Pancreas Committee to collect data on medical urgency status in pancreas patients.

In September 2023, the OPTN Board of Directors, in the process of establishing a working group on organ nonuse, discussed the kidney and pancreas continuous distribution project, and decided that the kidney and pancreas continuous distribution proposal would not be submitted for public comment in January 2024. The OPTN Kidney and Pancreas Committees were directed to evaluate the potential impact of continuous distribution on the following goals:

• decreased nonuse/nonutilization of kidneys and pancreata;

• decreased out-of-sequence allocation of kidneys; and

• consideration of expedited placement pathways for kidneys at a high risk of nonuse.

The Committees will continue to update the community with each public comment cycle on the project’s progress to date.

To summarize, the continuous distribution proposal for kidney and pancreas needs additional refinement before it is ready for implementation. Defining outcome criteria, establishing medical urgency criteria, and improving utilization while allowing for broader sharing without defined boundaries—and doing all of this without adversely affecting pancreas transplant volumes—continue to be challenges in the field of pancreas transplantation.

2 Waiting List

The number of adult candidates added to the waiting list in 2022 remained stable in comparison with the previous year for simultaneous pancreas-kidney (SPK) transplant (1,486 in 2022 compared with 1,487 in 2021) and for pancreas transplant alone (PTA) (180 in 2022 compared with 181 in 2021). However, the number of pancreas-after-kidney (PAK) transplant candidates added to the waiting list dropped notably (71 in 2022 compared with 106 in 2021) (Figure PA 1). The PAK category had a consistent decline in candidates year over year during the past decade. This decline in PAK listings corresponded with an increase in SPK listings during the same period, probably reflecting the shift in preference to performing deceased donor SPK transplants, where waiting times are shorter (Table PA 3 and Table PA 12), over doing a living donor kidney transplant followed by a deceased donor pancreas transplant, where waiting times are longer (Table PA 3 and Table PA 12).

Prevalent adult listings increased for SPK (3,340 in 2022 compared with 3,207 in 2021). Prevalent adult listings were stable for PTA (541 in 2022 compared with 543 in 2021) but decreased for PAK (356 in 2022 compared with 399 in 2021) (Figure PA 2).

The age distribution of adult candidates on the waiting list shows trends over the past decade that are unmistakable. The proportion of older candidates (55 years or older) increased steadily, to 14.8% in 2022 from 11.6% in 2011, possibly related to the increased proportion of candidates with type 2 diabetes being added to the list. There was a corresponding drop for the 45- to 54-year age group (30.2% in 2022 compared with 35.1% in 2011). The 35- to 64-year age group was stable (34.9% in 2022 compared with 35.4% in 2011), and the 18- to 34-year age group increased (20.2% in 2022 compared with 17.9% in 2011) (Figure PA 3).

The sex distribution of adult pancreas waitlist candidates remained stable over the past decade with a male preponderance of about 10% (54.1% male and 45.9% female in 2022) (Figure PA 4). The male preponderance is probably driven by the majority SPK candidate population, because the PTA candidate population has a higher proportion of women (Table PA 1).

In terms of race and ethnicity, the proportion of adult White candidates on the pancreas waiting list continued to drop over the past decade. For the first time, White candidates did not make up the majority of the list (48.1% in 2022 compared with 67.3% in 2011) (Figure PA 5). The proportions of Black and Hispanic candidates continued to increase (28.5% Black in 2022 compared with 18.0% in 2011; 16.9% Hispanic in 2022 compared with 11.5% in 2011). The proportion of Asian candidates also increased but made up a small portion of the list. The Multiracial and Native American populations remained stable.

Perhaps the most notable trend for the pancreas waiting list in the past few years is the increase in listings of adult candidates with type 2 diabetes, which reached its highest level (23.2% in 2022 compared with 7.8% in 2011), with a corresponding decrease in listings of candidates with type 1 diabetes (68.8% in 2022 compared with 83.3% in 2011) (Figure PA 6). This drove a number of other changes in characteristics on the waiting list, such as age, body mass index (BMI), and race and ethnicity. For example, the proportion of candidates with obesity (BMI > 30 kg/m²) increased over the past decade (23.2% in 2022 compared with 18.3% in 2011), while the proportion of candidates with a BMI of less than 25 kg/m² decreased (36.0% in 2022 compared with 42.8% in 2011) (Figure PA 8).

The distribution of adult candidates by waiting time shifted toward a higher proportion waiting 1-<2 years compared with those waiting less than 1 year (Figure PA 7). This shift might be due to the increase in prevalent listings with a gradual move toward longer waiting times.

The distribution of candidates by blood type was largely unchanged year over year from 2021 to 2022; in 2022, 47.2% of candidates had blood type O, 33.0% had type A, 16.2% had type B, and 3.7% had type AB. The 16.2% value for candidates with blood type B, however, represents a gradual increase in prevalence over the past decade (from 12.8% in 2011) (Figure PA 9).

With regard to transplant type, the waiting list in 2022 comprised predominately SPK candidates (78.8%), followed by PTA (12.8%) and PAK candidates (8.4%). The upward trend of SPK candidates, the decline of PAK candidates, and the stable proportion of PTAs has been the pattern over the past few years (Figure PA 10).

The proportion of adult retransplant candidates continued to decrease, to 7.0% in 2022 compared with 15.3% in 2011 (Figure PA 11). Historically, PAK candidates have been the most likely to have had a prior pancreas or kidney-pancreas transplant (Table PA 3); therefore, the overall drop in PAKs (Figure PA 10) has impacted the overall retransplant candidate rate as well.

Overall pancreas transplant rates among adult candidates have seen a decreasing trend since 2019, after an increasing trend for several years prior. The transplant rate in 2022 was 36.7 transplants per 100 patient-years, down from 40.2 in 2021 and the peak of 44.8 in 2019 (Figure PA 12). Initially it was thought that the drop after 2019 was attributable to the COVID-19 pandemic; however, the continued decline implies that other factors, such as more stringent criteria for pancreas donation and acceptance, are involved. Of note, this decrease in the transplant rate was most pronounced in candidates with type 2 diabetes (38.5 transplants per 100 patient-years in 2022 compared with 52.2 in 2021) (Figure PA 13). This suggests that centers may be using a higher threshold for organ acceptance for the older, higher BMI candidates. This could also partly be a function of a larger number of candidates with type 2 diabetes being added to the list.

The decrease in transplant rate in adults does not affect any blood type disproportionately compared with the past few years (Figure PA 14). Of note, the drop in overall transplant rates is not as apparent in candidates intended for PAK transplant, where the rates have been stable over the past 4 years, albeit at smaller numbers (Figure PA 15).

Three-year outcomes for adult candidates added to the waiting list from 2017 through 2019 show that among candidates for SPK transplant, most underwent transplant (61.4% with a deceased donor pancreas and kidney, 4.5% with a living donor kidney and deceased donor pancreas), 11.3% were still waiting, 5.2% died while waiting, and 17.5% were removed from the list (Figure PA 18). Among candidates for PTA, 46.6% underwent transplant, 21.0% were still waiting, 3.0% died, and 29.5% were removed from the list (Figure PA 17). Among candidates for PAK transplant, 32.3% underwent transplant, 29.4% were still waiting, 1.7% died, and 36.6% were removed from the list (Figure PA 16); note that the proportion removed from the list exceeded the proportion who underwent transplant.

Mortality on the waiting list has steadily decreased among adults since the peak in 2020 (6.2 deaths per 100 patient-years), down to 4.7 in 2022 (Figure PA 19). This 2020 peak is partly attributable to the COVID-19 pandemic. An exception to the decrease in mortality rate was among candidates for PTA, where it increased to 3.4 deaths per 100 patient-years in 2022 from 2.7 in 2021 (Figure PA 23), although this may be insignificant given the small numbers of PTA candidates. Another exception to the trend of decreasing waitlist mortality was among older candidates (55 years or older), where the rate increased to 8.9 deaths per 100 patient-years in 2022 from 6.7 in 2021 (Figure PA 20).

There were no notable trends in waitlist mortality by race and ethnicity (Figure PA 21), although year over year there was a slight decrease in mortality in Black candidates (4.1 deaths per 100 patient-years in 2022 compared with 5.6 in 2021), a slight increase in Hispanic candidates (4.4 deaths per 100 patient-years in 2022 compared with 3.7 in 2021), and, although they make up a smaller number on the waiting list (Table PA 1), a notable increase in Asian candidates (6.2 deaths per 100 patient-years in 2022 compared with 2.8 in 2021). No notable differences were found in waitlist mortality rates between male and female candidates (Figure PA 22). There were wide geographic variances across donation service areas in waitlist mortality ranging from 0.0 to 31.6 deaths per 100 patient-years, but these should be interpreted with caution since some donation service areas may have small numbers (Figure PA 24).

Deaths within 6 months after removal from the waiting list among adults increased year over year to 8.5% in 2022 from 6.8% in 2021 (Figure PA 25). This is also a notable increase from 4.9% in 2011, although this number has oscillated over the past decade. Surprising findings in the increase in deaths after waitlist removal were that it was quite pronounced in the younger age groups (18-34 and 35-44 years) and less pronounced in the older age group (55 years or older) and that deaths after waitlist removal actually decreased notably among 45- to 54-year-olds in 2022 compared with 2021 (Figure PA 26). These data should be watched closely in the upcoming years to note if there is a new trend. As expected, the SPK candidates had the highest proportion of deaths within 6 months after waitlist removal (11.7% in 2022), which was a pronounced increase from the previous year. Death after waitlist removal in 2022 among PAK candidates (0.0%) and among PTA candidates (2.9%) decreased from the previous year (Figure PA 27).

Regarding distance, 80% or more of SPK and PAK candidates live within 100 miles of the transplant center, whereas PTA candidates may travel farther, with 36.9% living outside of a 100-mile radius of the transplant center (Table PA 1).

3 Donations

The number of deceased donors whose pancreata were recovered for pancreas transplant was 1,285 in 2022, down from 1,307 in 2021 and 1,500 in 2011 (Figure PA 28). Consequently, this correlated with fewer pancreas transplants in 2022 (Figure PA 40). The younger age groups of donors (younger than 18 and 18-29 years) showed a decreasing trend as a percent of total donors over the past 3 years, while older donors showed a corresponding increase (Figure PA 29). The male-to-female ratio of pancreas donors remained largely unchanged with a male preponderance in 2022: 68.9% male and 31.1% female (Figure PA 30). The racial and ethnic distribution of donors also remained steady over the past 3 years, with 59.5% White, 19.6% Black, 16.8% Hispanic, 2.7% Asian, and 1.4% Other (Multiracial and Native American) in 2022 (Figure PA 31). By BMI, the large majority of donors (85.5%) were in the BMI 18.5-<30 range, a proportion largely unchanged in the past few years (Figure PA 32). Within this range, however, there was a slight shift toward the BMI 25-<30 group (30.9%) from the BMI 18.5-<25 group (54.6%) compared with the past 2 years. Of note, extremes of BMI were still considered for pancreas donation (7.0% BMI <18.5 and 7.5% BMI >30 in 2022), although one could reasonably assume the nonuse rate is likely to be higher, at least in the higher BMI group.

Considering donor cause of death, the opioid epidemic appears to still contribute to a continued increase in anoxic brain injury, with a record 40.8% of donors in 2022 dying of anoxia. Head trauma as a cause of death had a corresponding proportional decrease to 47.1% of donors in 2022 (Figure PA 33). Other donor causes of death remained largely unchanged.

The nonuse rate of pancreata, defined as pancreata recovered for transplant but not transplanted, inched up in 2022 to 28.6%, its highest level since 2011 (Figure PA 34). Pancreas continued to have one of the highest nonuse rates among organs, likely due to a combination of factors. As expected, the nonuse rate was highest, at 100% in 2022, for donors older than 55 years and dropped almost linearly as donor age decreased (Figure PA 35). The proposed continuous distribution pancreas allocation policy currently under development would give increased priority to pancreas islet candidates, a very small proportion of the pancreas waiting list, for pancreata from donors aged 45 years and older; therefore, it will be of interest to look at the implications for pancreas utilization above this age for future analyses. The male-to-female distribution of pancreas nonuse did not change in 2022 and has remained largely unchanged in the past 5 years (Figure PA 36). The distribution of pancreata that were not used was fairly stable between the Black, White, and Hispanic racial and ethnic groups in 2022 compared with 2021 (Figure PA 37) but increased in the Asian and Other (Multiracial and Native American) donor groups; however, this might not be significant due to the small numbers. As expected, high-BMI donors had the highest nonuse rates in 2022 (83.3% for BMI 35-<40 and 42.9% for BMI 30-<35), and from there it decreased with decreasing BMI, with the lowest nonuse rate in the BMI <18.5 group at 15.6% (Figure PA 38). The Public Health Service (PHS) risk criteria for acute transmission of HIV, hepatitis B virus (HBV), or hepatitis C virus (HCV) did not seem to affect acceptance of pancreas offers; donors with risk factors for acute transmission of HIV, HBV, or HCV actually had a lower nonuse rate (23.9%) versus donors who did not have risk factors for disease transmission (29.5%) in 2022 (Figure PA 39). More accurate and time-sensitive testing methods and community education have contributed to improving the use of donors with PHS risk factors for disease transmission in the past few years.

4 Transplants

The overall number of pancreas transplants (including adult and pediatric) continued to decrease, with the lowest reported number in the past decade at 918 in 2022 (Figure PA 40). Following stabilization of the overall number of pancreas transplants in 2021 nearing the end of the COVID-19 pandemic, the number of pancreas transplants continued to decrease in all transplant categories, with the most pronounced decrease in PTA: 62 in 2022 from 92 in 2021 (Figure PA 41).

The previous trend toward increases in the total number of pancreas transplants in recipients older than 45 years reversed in 2022, but there were increases in the number of pancreas transplants in recipients in the 18-34 and 35-44 year age groups (Figure PA 42). The male-to-female ratio of pancreas transplant recipients has been consistent over the past decade, with more male than female recipients (Figure PA 43). The number of pancreas transplants performed in White recipients continued to decrease in 2022 while the number of pancreas transplants performed in Black and Hispanic recipients increased (Figure PA 44). The relative increase in the number of pancreas transplants in Hispanic recipients over the past decade corresponds to an increase in the number of pancreas transplants performed for recipients with type 2 diabetes. The number of pancreas transplants in recipients with type 2 diabetes increased by 221.9% from 2011 to 2022 (from 64 to 206), whereas the number of transplants for recipients with type 1 diabetes decreased by 29.6% from 2011 to 2022 (from 900 to 634). Nonetheless, there was a small drop in the proportion of pancreas transplants in recipients with type 2 diabetes in the past year, where 22.4% of pancreas transplants in 2022 were in recipients with type 2 diabetes compared with 25.8% in 2021 (Figure PA 45).

The proportion of pancreas transplants in adults that used induction with T-cell depletion alone has increased to 86.3% in 2022 from 76.1% in 2011, while the proportion of pancreas transplants using induction with interleukin-2 receptor antibody alone has decreased to 3.7% in 2022 from 8.2% in 2011 (Figure PA 46). The maintenance immunosuppressive regimens following pancreas transplant have remained consistent, with most centers using tacrolimus and mycophenolate mofetil plus or minus steroids (Figure PA 47). There were further decreases in the use of steroid-free maintenance regimens, with 22.8% reporting a steroid-free tacrolimus and mycophenolate regimen in 2022, nearly the lowest frequency for the past decade (Figure PA 47). The cPRA levels in pancreas transplants recipients has been relatively consistent over the past decade, with unsensitized recipients and recipients with cPRA of less than 20% constituting most of the transplants (Figure PA 48, Figure PA 49, and Figure PA 50), corresponding to incidences of acute rejection of less than 12% (Figure PA 62 and Figure PA 63).

The increases in the proportion of pancreas transplants performed in adults at medium-volume centers (11-24 transplants per year) noted in 2021 (48.3%) were reversed in 2022 (37.2%), with a corresponding notable increase in the proportion of pancreas transplants performed at large-volume centers (25 or more transplants per year; 15.9% in 2021 and 25.3% in 2022) and a slight increase in the proportion of pancreas transplant centers that performed fewer than 10 transplants per year (Figure PA 51 and Figure PA 52).

5 Outcomes

The incidence of pancreas graft failure among adults within the first 90 days following SPK, likely reflecting early technical losses, remained low at 6.1% (Figure PA 53). Early graft loss proportions decreased in 2022 for PAK (to 5.3% in 2022 from 8.0% in 2021) and PTA (to 8.8% in 2022 from 16.3% in 2021). Of importance, the incidence of pancreas graft failure within the first year posttransplant was lower in SPK and PAK transplant, with an incidence of 8.1% following SPK in 2021 and 10.0% following PAK in 2021. The incidence of pancreas graft failure in the first year posttransplant was higher following PTA, increasing to 20.4% after PTA in 2021 from 15.6% after PTA in 2020 (Figure PA 54). These are important data, because the present 2022 Annual Data Report reflects the third year that the new definition of pancreas graft failure has been in effect. Prior to 2020, there were no strict criteria for defining pancreas graft failure, and, as a result, only patient survival was reported. However, starting in 2020, the criteria for pancreas graft loss were clearly defined, and included any of the following: 1) a recipient’s transplanted pancreas is removed; 2) a recipient reregisters for a pancreas transplant; 3) a recipient registers for an islet transplant after undergoing a pancreas transplant; 4) a recipient dies; or 5) a recipient’s total insulin use is greater than or equal to 0.5 units/kg/day for 90 consecutive days (OPTN Policy 1.2: definitions). Since the SRTR started reporting pancreas graft failure using these more granular definitions in 2020, the incidence of pancreas graft loss within the first year posttransplant remained very low for SPK and PAK recipients (Figure PA 53 and Figure PA 54).

The all-cause unadjusted kidney failure rates among adults at 1, 5, and 10 years posttransplant are 4.3%, 14.1%, and 35.0%, respectively, following SPK transplant for the most recent data available (Figure PA 55). This long-term kidney graft success in part reflects the low (excellent) kidney donor profile index of the kidneys typically used for SPK transplant, but it also can be attributed to the normalization of hemoglobin A_1c with pancreas transplant and the associated prevention of recurrent diabetic nephropathy. The merits of providing normalization of hemoglobin A_1c on long-term kidney function are highlighted by the low rate of 10-year death-censored kidney graft failure at 19.8% among adult SPK recipients for transplants in 2012, the most recent year of data available (Figure PA 56). The benefits of consistent normoglycemia on the longevity of the kidney allograft are further reinforced by the low 10-year death-censored rates of kidney graft failure following PAK of 16.5% and 14.7% with deceased and living donor kidneys, respectively, for transplants in 2012-2013, the most recent years of data available (Figure PA 58 and Figure PA 60).

The incidence of acute rejection during the first year following pancreas transplant in adults has been consistently low for the past decade, with rates of 11.4%, 9.0%, and 10.9% for recipients aged 18-34, 35-49, and 50-64 years, respectively (Figure PA 62). The consistency of the immunosuppressive regimens over the past 5 years (Figure PA 46 and Figure PA 47) reflects the success of immunosuppression in overcoming both the alloimmune and autoimmune responses following pancreas transplant. Historically, the incidence of acute rejection during the first year following pancreas transplant was lower when the reported induction agent was lymphodepleting, although this was not observed in the data from 2021. These data showed an incidence of acute rejection at 11.1% and 10.2% following induction with a nonlymphodepleting versus lymphodepleting agent, respectively (Figure PA 63). Despite the more aggressive immunosuppressive regimens used following pancreas transplant and the associated low incidence of rejection, note that the rate of posttransplant lymphoproliferative disorder (PTLD) has remained consistently low during the 5 years after SPK and is dependent on the Epstein-Barr virus (EBV) status of the donor and the recipient. For SPK recipients, there was a PTLD incidence of 1.6% in EBV-negative recipients compared with an incidence of 0.62% in EBV-positive recipients (Figure PA 66). The disparity between EBV-negative and EBV-positive recipients was most pronounced for the recipients who underwent PTA, with a 5-year incidence of 6% in EBV-negative recipients versus 0.7% in EBV-positive recipients (Figure PA 65). The relatively high incidence of PTLD in EBV-negative recipients following PTA is consistent with the more aggressive immunosuppression required following pancreas transplant in the nonuremic recipient.

The rates of recipient mortality at 1 year following pancreas transplant have been consistently low for the past decade, with the most recent data showing rates of 2.5%, 1.3%, and 3.7% for PAK, PTA, and SPK, respectively (Figure PA 67). The low 1-year mortality rates reflect the relative safety of this procedure, despite the technical and immunosuppressive challenges associated with pancreas transplant. Ten-year mortality rates of 22.1%, 17.6%, and 23.7% for PAK, PTA, and SPK, respectively, for transplants in 2012-2013, the most recent available data, are likely the result of the cardiovascular comorbidities that were present at the time of the pancreas transplant in this cohort of recipients with long-standing diabetes (Figure PA 69). Of interest, the 5-year patient survival percentages following pancreas transplant in recipients with type 1 (91.9%) versus type 2 (87.3%) diabetes are comparable (Figure PA 71). It will be important to determine the impact of diabetes type on long-term pancreas allograft outcome using the more granular definitions of allograft success. These data will be key for getting a better understanding of which recipients with type 2 diabetes will benefit from SPK versus kidney transplant alone.