Equivalent success of simultaneous pancreas kidney and solitary pancreas transplantation. A prospective trial of tacrolimus immunosuppression with percutaneous biopsy

Tacrolimus: a further update of its pharmacology and therapeutic use in the management of organ transplantation

Tacrolimus (FK-506) is an immunosuppressant agent that acts by a variety of different mechanisms which include inhibition of calcineurin. It is used as a therapeutic alternative to cyclosporin, and therefore represents a cornerstone of immunosuppressive therapy in organ transplant recipients. Tacrolimus is now well established for primary immunosuppression in liver and kidney transplantation, and experience with its use in other types of solid organ transplantation, including heart, lung, pancreas and intestinal, as well as its use for the prevention of graft-versus-host disease in allogeneic bone marrow transplantation (BMT), is rapidly accumulating. Large randomised nonblind multicentre studies conducted in the US and Europe in both liver and kidney transplantation showed similar patient and graft survival rates between treatment groups (although rates were numerically higher with tacrolimus- versus cyclosporin-based immunosuppression in adults with liver transplants), and a consistent statistically significant advantage for tacrolimus with respect to acute rejection rate. Chronic rejection rates were also significantly lower with tacrolimus in a large randomised liver transplantation trial, and a trend towards a lower rate of chronic rejection was noted with tacrolimus in a large multicentre renal transplantation study. In general, a similar trend in overall efficacy has been demonstrated in a number of additional clinical trials comparing tacrolimus- with cyclosporin-based immunosuppression in various types of transplantation. One notable exception is in BMT, where a large randomised trial showed significantly better 2-year patient survival with cyclosporin over tacrolimus, which was primarily attributed to patients with advanced haematological malignancies at the time of (matched sibling donor) BMT. These survival results in BMT require further elucidation. Tacrolimus has also demonstrated efficacy in various types of transplantation as rescue therapy in patients who experience persistent acute rejection (or significant adverse effect's) with cyclosporin-based therapy, whereas cyclosporin has not demonstrated a similar capacity to reverse refractory acute rejection. A corticosteroid-sparing effect has been demonstrated in several studies with tacrolimus, which may be a particularly useful consideration in children receiving transplants. The differences in the tolerability profiles of tacrolimus and cyclosporin may well be an influential factor in selecting the optimal treatment for patients undergoing organ transplantation. Although both drugs have a similar degree of nephrotoxicity, cyclosporin has a higher incidence of significant hypertension, hypercholesterolaemia, hirsutism and gingival hyperplasia, while tacrolimus has a higher incidence of diabetes mellitus, some types of neurotoxicity (e.g. tremor, paraesthesia), diarrhoea and alopecia.

CONCLUSION

Tacrolimus is an important therapeutic option for the optimal individualisation of immunosuppressive therapy in transplant recipients.

Islet cell damage associated with tacrolimus and cyclosporine: morphological features in pancreas allograft biopsies and clinical correlation

BACKGROUND

The introduction of the potent immunosuppressive drugs tacrolimus (FK) and cyclosporine (CSA) has markedly improved the outcome of solid organ transplantation. However, these drugs can cause posttransplantation diabetes mellitus. Abnormalities in the glucose metabolism are of particular significance in pancreas transplantation.

METHODS

We studied 26 pancreas allograft biopsies, performed 1-8 months posttransplantation, from 20 simultaneous kidney-pancreas transplant recipients, randomized to receive either FK or CSA. The biopsies were studied by light microscopy, immunoperoxidase stains for insulin and glucagon, in situ DNA-end labeling for detection of apoptosis, and electron microscopy. The islet morphology was correlated with the mean and peak levels of CSA and FK in serum, with corticosteroid administration and with glycemia.

RESULTS

On light microscopy cytoplasmic swelling, vacuolization, apoptosis, and abnormal immunostaining for insulin were seen in biopsies from patients receiving either FK or CSA. The islet cell damage was more frequent and severe in the group receiving FK than in the group receiving CSA (10/13 and 5/13, respectively) but the differences were not statistically significant. Significant correlation was seen between the presence of islet cell damage and serum levels of CSA or FK during the 15 days previous to the biopsy, as well as with the peak level of FK. Toxic levels of CSA or FK and administration of pulse steroids were associated with hyperglycemia when these occurred concurrently (P=0.005). Toxic levels of CSA or FK by themselves were associated with hyperglycemia in a minority of cases (8 and 26%, respectively). Electron microscopy showed cytoplasmic swelling and vacuolization, and marked decrease or absence of dense-core secretory granules in beta cells; the changes were more pronounced in patients on FK. Serial biopsies from two hyperglycemic patients receiving FK and evidence of islet cell damage demonstrated reversibility of the damage when FK was discontinued.

CONCLUSIONS

The structural damage to beta cells demonstrated in this study is similar to morphological and functional abnormalities previously described in experimental animal models and can at least partially account for the glucose metabolism abnormalities seen in patients receiving these drugs. Toxic levels of CSA or FK and higher steroid doses potentiate each others' diabetogenic effects.

Mycophenolate mofetil and tacrolimus as primary maintenance immunosuppression in simultaneous pancreas-kidney transplantation: initial experience in 50 consecutive cases

BACKGROUND

The current study examines the use of mycophenolate mofetil (MMF) and tacrolimus as primary immunosuppression in simultaneous pancreas-kidney (SPK) transplantation. In addition, analyses of the rates of conversion from one immunosuppressive agent to another, and its subsequent consequences with respect to outcomes were determined. Quality of graft function, infections, and effect on preexisting essential hypertension are also described.

METHODS

Immunosuppression consisted of quadruple therapy with antithymocyte globulin induction, tacrolimus, MMF, and prednisone. Patient and graft survival and rejection rates in 50 consecutive SPK recipients, followed for a minimum of 3 months and a mean of 14 months (range: 3-34 months), are described.

RESULTS

Thirty-nine of 50 (78%) patients tolerated the MMF/tacrolimus combination long-term (mean duration of follow-up: 14+/-7 months). Nine of 50 patients (18%) were converted to Neoral, and 4 patients were converted to azathioprine as a substitute for MMF. The 2-year actuarial patient, kidney, and pancreas survival rates were 97.7%, 93.3%, and 90.0%, respectively. At 6 months after transplant, the overall incidence of acute rejection was 16%. There was a statistically significant (P< or =0.04, Cox-Mantel test) difference in the rate of rejection associated with conversion to Neoral. The incidence of rejection 6 months after transplant in the group maintained on MMF/tacrolimus was 10.2% vs. 44.4% in the group converted to Neoral (P< or =0.04, Cox-Mantel test). Overall, the 1-year actuarial cumulative incidence of tissue-invasive cytomegalovirus disease was 6.6%. There were no cases of fungal infections or post-transplant lymphoproliferative disorders. One patient developed Kaposi's sarcoma 10 months after transplant. With respect to hypertensive disease, 60% (12/20) of the patients who required pharmacologic control of blood pressure before transplant were off all antihypertensive medications at 1 year after transplant. An additional 20% (4/20) of patients had a reduction in the number of medications required to control blood pressure at 1 year after transplant.

CONCLUSIONS

We conclude that the combination of MMF and tacrolimus as primary immunosuppression for SPK transplantation results in excellent patient and graft survival rates, a very low rate of acute rejection, and low rates of infection and malignancy.

Acute pancreatic transplant rejection: evaluation with dynamic contrast-enhanced MR imaging compared with histopathologic analysis

PURPOSE

To evaluate the use of dynamic contrast material-enhanced gradient-recalled-echo MR imaging for the diagnosis of acute pancreatic transplant rejection, as confirmed at histopathologic analysis.

MATERIALS AND METHODS

Thirty MR imaging studies were performed in 25 patients within 3 days of percutaneous biopsy or pancreatectomy. The mean percentage of parenchymal enhancement (MPPE) at dynamic contrast-enhanced MR imaging was calculated.

RESULTS

Biopsy findings were no evidence of rejection (n = 7 [23%]), mild rejection (n = 10 [33%]), moderate (n = 6 [20%]) and severe (n = 2 [7%]) acute rejection, and infarction (n = 5 [17%]). The corresponding MPPEs at 1 minute were 106%, 66%, 62%, 57%, and 3%, respectively. Overlap of cases in the normal and rejection groups occurred; however, using an MPPE cutoff of 100% resulted in a sensitivity of 96%. An MPPE over 120% was seen in the normal group only. The MPPE was significantly greater in the normal group than in the rejection or infarction group (P < .05).

CONCLUSION

Dynamic contrast-enhanced MR imaging is highly sensitive for the detection of acute pancreatic transplant rejection. Because of overlap of cases in the normal and rejection groups, percutaneous biopsy may be needed in some cases. Pancreatic allografts with infarction can be clearly identified.

Review of immunosuppressive usage in pancreas transplantation

Throughout 1997, nearly 10,000 pancreas transplants have been performed worldwide, with 88% being simultaneous kidney transplants (SKPT). The current 1 yr patient survival rate exceeds 90% and pancreas graft survival (complete insulin independence) rate exceeds 80% for SKPT, 70% for sequential pancreas after kidney transplant (PAKT), and 65% for pancreas transplant alone (PTA). According to registry data, rejection accounts for 32% of graft failures in the first year after pancreas transplantation. However, improvements are expected to continue with the evolution of treatment protocols. Most pancreas transplant centers employ quadruple drug immunosuppression with anti-lymphocyte induction with either a monoclonal or polyclonal antibody agent. In recent years, there has been an overall decline in the use of antibody induction therapy from 90% during the period 1987-1993 to 83% of pancreas transplants performed during 1994-1997. Maintenance immunosuppression is triple therapy consisting of a calcineurin inhibitor (cyclosporine or tacrolimus), corticosteroids, and an anti-metabolite (AZA or MMF). Prior to 1995, nearly all pancreas transplant recipients were managed with Sandimmune. In the last 2 yr, tacrolimus-based therapy has been used in approximately 20% of cases and a new microemulsion formulation of cyclosporine (Neoral) has replaced Sandimmune in contemporary post-transplant immunosuppression. In addition, MMF is replacing AZA as part of the standard immunosuppressive regimen after pancreas transplantation. At present, a number of centers are conducting various trials with new drug combinations including either Neoral or tacrolimus in combination with steroids and MMF with or without antibody induction therapy. From 1994 to 1997, the 1 yr rates of immunologic graft loss have decreased to 2% after SKPT, 9% after PAKT, and 16% after PTA. The current array of new immunosuppressive agents are providing more effective control of rejection and permitting solitary pancreas transplantation to become an accepted treatment option in diabetic patients without advanced complications. The apparent potency of new drug combinations has also resulted in a resurgence of interest in steroid withdrawal. Immunosuppressive strategies will continue to evolve in order to achieve effective control of rejection while minimizing 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. Pancreas transplantation will remain an important alternative in the treatment of diabetic patients until other strategies are developed that can provide equal glycemic control with less immunosuppression and overall morbidity.

Long-term results of pancreas transplantation under tacrolius immunosuppression

BACKGROUND

The long-term safety and efficacy of tacrolimus in pancreas transplantation has not yet been demonstrated. The observation of prolonged pancreatic graft function under tacrolimus would indicate that any potential islet toxicity is short-lived and clinically insignificant. We report herein the results of pancreas transplantation in patients receiving primary tacrolimus immunosuppression for a minimum of 2 years.

METHODS

From July 4, 1994 until April 18, 1996, 60 patients received either simultaneous pancreas-kidney transplant (n=55), pancreas transplant only (n=4), or pancreas after kidney transplantation (n=1). Baseline immunosuppression consisted of tacrolimus and steroids without antilymphocyte induction. Azathioprine was used as a third agent in 51 patients and mycophenolate mofetil in 9. Rejection episodes within the first 6 months occurred in 48 (80%) patients and were treated with high-dose corticosteroids. Antilymphocyte antibody was required in eight (13%) patients with steroid-resistant rejection.

RESULTS

With a mean follow-up of 35.1+/-5.9 months (range: 24.3-45.7 months), 6-month and 1-, 2-, and 33-year graft survival is 88%, 82%, 80%, and 80% (pancreas) and 98%, 96%, 93%, and 91% (kidney), respectively. Six-month and 1-, 2-, and 3-year patient survival is 100%, 98%, 98%, and 96.5%. Mean fasting glucose is 91.6+/-13.8 mg/dl, and mean glycosylated hemoglobin is 5.1+/-0.7% (normal range: 4.3-6.1%). Mean tacrolimus dose is 6.5+/-2.6 mg/day and mean prednisone dose 2.0+/-2.9 mg/day at follow-up. Complete steroid withdrawal was possible in 31 (65%) of the 48 patients with functioning pancreases.

CONCLUSIONS

These data show for the first time that tacrolimus is a safe and effective long-term primary agent in pancreas transplantation and provides excellent long-term islet function without evidence of toxicity while permitting steroid withdrawal in the majority of patients.

Strategies to expand the donor pool for pancreas transplantation

BACKGROUND

Our organ procurement organization has been forced to liberalize the donor criteria in order to expand the donor pool for pancreas transplantation. In this report, we describe our experience using whole organ pancreatic grafts from "marginal" donors, which include grafts obtained from donors over 45 years of age and from donors who were identified to be hemodynamically unstable at the time of organ retrieval.

METHODS

A prospective study was performed between July 1994 and March 1998, during which time 137 pancreas transplants were performed at our center using organs procured by our own surgeons (organs sent by other teams were excluded). The rapid en bloc technique was used exclusively. The use of pancreatic grafts from marginal donors was analyzed for short-term and overall graft survival, and for delayed graft function and complications.

RESULTS

Overall pancreas graft survival for our series was 83%, with a mean follow-up of 23 months. There were 22 pancreas grafts from donors over 45 years of age, 13 of whom were greater than 50 years of age. The actual graft survival rate of the over-45 donor group was 86%. Fifty-one grafts were removed from hemodynamically unstable donors on high-dose vasopressors. The actual graft survival in this group was 86%. There was no significant difference found in graft survival between recipients of pancreatic grafts from marginal and nonmarginal donors. Delayed graft function was exhibited by more recipients of grafts from donors on high-dose vasopressors (P<0.05), but this had no effect on long-term graft survival and endocrine function. Recipients of marginal donor grafts did not have higher rates of complication compared to recipients of nonmarginal grafts.

CONCLUSIONS

Based on our results, we currently employ a graft selection strategy not limited by donor age or hemodynamic stability. Our selection of pancreas organs for transplantation is based on careful inspection of the pancreas and determination of the adequacy of the ex vivo flush. Our results suggest that the current pancreas donor pool may be expanded substantially.

Simultaneous pancreas-kidney transplantation: an overview of indications, complications, and outcomes

Simultaneous pancreas-kidney transplantation (SPK) has become an accepted therapy for the treatment of patients with insulin-dependent diabetes mellitus and renal failure from diabetic nephropathy. The procedure has evolved over the last twenty years, and refinements in technique, better organ preservation solutions, and more potent immunosuppressive therapies have improved one-year graft-survival rates to 81% for the pancreas and 88% for the kidney (International Pancreas Transplant Registry Data-1996). Proper patient selection is important, given the increased complexity of the procedure, the increased need for immunosuppression, and the need for compliance with postoperative medications and monitoring. The benefits of a successful SPK include more physiologic glucose metabolism and freedom from dialysis. This review will describe the indications and selection process for potential candidates, outline the procedure and postoperative care, and discuss the potential impact on secondary complications of diabetes mellitus. It will then discuss results and complications from the use of current protocols and immunosuppression at the University of California at San Francisco.

Pancreas transplantation

Although intensified insulin therapy regimens enable normalization of blood glucose levels and related metabolic parameters, these regimens are associated with an increased incidence of hypoglycemic episodes. Pancreas transplantation has achieved the goal of providing insulin independence with stable and continuous normoglycemia. But because of the associated morbidity and mortality and the need for life-long immunosuppression after transplant, it is difficult to justify pancreas transplantation in diabetic patients at a pre-uremic stage. Pancreas transplantation is therefore performed in conjugation with renal transplantation. The majority of renal transplant centers, however, have been reluctant to perform simultaneous kidney-pancreas transplantation in insulin-dependent uremic patients because of the additional risks associated with pancreas transplantation. More recently, refinements in surgical technique, introduction of new immunosuppressive agents, and better selection of transplant candidates have contributed to improved survival. Today, combined pancreas-kidney transplantation is an accepted treatment for carefully selected patients with insulin dependent diabetes and end-stage renal disease and in a small group of patients with uncontrolled severe metabolic problems. The effect of a euglycemic state after pancreas transplantation on the progression of micro- and macroangiopathy remains to be proved, although recently there is evidence to suggest that some end-organ lesions may be halted or even ameliorated. Further improvement in anti-rejection strategies may achieve better long-term graft survival and provide the incentive to perform pancreas transplantation at an earlier stage, before severe secondary complications of diabetes develop.

Histologic grading of acute allograft rejection in pancreas needle biopsy: correlation to serum enzymes, glycemia, and response to immunosuppressive treatment

BACKGROUND

Allograft rejection continues to be the most common cause of graft failure in technically successful pancreas transplants. Early diagnosis and treatment of rejection is essential for long-term graft survival. Pancreas graft biopsies are now used routinely for the diagnosis of acute allograft rejection. The correlation between clinical evidence of graft dysfunction (increased serum enzymes and glucose), severity of acute rejection on biopsy (rejection grade), and response to treatment has not been previously studied.

METHODS

A total of 151 pancreas transplant needle biopsy specimens from 57 patients were evaluated. Statistical correlation was done between the histologic rejection grade (O-V) and the peak level of enzymes in serum, glycemia, type of antirejection treatment instituted, and response to treatment. Differentiation between grades was also evaluated statistically.

RESULTS

Response to antirejection treatment was 25%, 40%, 88%, 78%, 50%, and 17% for grades O-V, respectively. The response for grades II and III was better than for grades 0-I and IV-V (P=0.0003 and 0.0008, respectively). The response to corticosteroids alone was 36%, 86%, 68%, and 0% for grades I, II, III, and IV, respectively. The response to antilymphocyte regimen was 50%, 89%, 85%, 71%, and 17% for grades I, II, III, IV, and V, respectively. Overall correlation between the mean levels of enzymes and rejection grade was seen; the increase of lipase was statistically significant (r=0.24, P=0.012). Amylase and lipase correlated very well with each other (r=0.84, P=0.0001). No correlation was found in the mean values of blood glucose with the serum enzyme increase and with severity of rejection. Hyperglycemia was present in 12 patients; this abnormality in patients with grades II-IV responded promptly to treatment, whereas in patients with grade V, hyperglycemia persisted despite antirejection treatment. Other causes of increased enzymes were found in patients with biopsy specimens showing no rejection (grades 0 and I, 43% and 31%, respectively).

CONCLUSIONS

Increased serum enzymes, particularly lipase, correlate with the grade of acute rejection, but their lack of specificity precludes their use as sole markers of acute rejection. Glucose levels are not a sensitive marker for acute rejection. Rejection grades II and III are the most responsive to treatment, and a significant proportion of these cases respond to treatment with corticosteroids only. The higher rejection grades (IV and V) require treatment with antilymphocytic regimens, and their overall response to treatment is moderate to poor, respectively.

Randomized comparison of triple therapy and antithymocyte globulin induction treatment after simultaneous pancreas-kidney transplantation

BACKGROUND

The incidence of acute rejection is considered to be higher after simultaneous pancreas-kidney (SPK) transplantation as compared to renal transplant alone. Therefore, the majority of SPK transplant recipients commonly receive a combination of cyclosporine (CsA) or tracolimus, and azathioprine or mycophenolic mofetyl, corticosteroids and/or antilymphocyte preparations. This study was designed to compare two immunosuppressive protocols for the prevention of acute rejection in patients undergoing SPK transplantation. The primary end-point was the incidence of acute rejection during the first 12 months after transplantation

METHODS

Fifty patients with type-I insulin-dependent diabetes and chronic renal failure were randomized to receive a triple drug immunosuppressive regimen including CsA, azathioprine and corticosteroids (N = 25), or the quadruple sequential combination of rabbit antithymocyte globulin (ATG) given for 10 days, azathioprine, corticosteroids and delayed CsA (N = 25). Maintenance immunosuppression (CsA and azathioprine, without corticosteroids) was similar in both arms.

RESULTS

The average follow-up was 36 months in both groups (range 9 to 60 months). No patient was excluded from the study. Although the percentage of patients with adverse events was higher in the ATG group (80 vs. 40%, P < 0.01), none of them resulted in premature discontinuation of the drug. Patients receiving ATG experienced a lower incidence (36% vs. 76%, P < 0.01) and number (13 vs. 29, P < 0.05) of acute renal rejection episodes. However, no difference was observed in patient, pancreas and kidney survival rates between groups. No case of isolated pancreas rejection was observed.

CONCLUSIONS

The quadruple sequential combination ATG, azathioprine, corticosteroid and CsA significantly reduced the one year incidence of acute renal rejection after SPK transplantation, compared to a triple immunosuppressive regimen.

Epstein-Barr virus-related posttransplantation lymphoproliferative disorder involving pancreas allografts: histological differential diagnosis from acute allograft rejection

The clinical and pathological features of acute pancreas allograft rejection and involvement of the graft by posttransplantation lymphoproliferative disorders (PTLD) overlap. Because the treatment is diametrically opposite in these two types of lesions, an accurate diagnosis is essential. The histological features in pancreas allograft needle biopsy specimens (n=7) and pancreatectomies (n=4) from four patients with Epstein-Barr virus (EBV)-related PTLD were compared with the material from 14 patients who did not develop PTLD after 12 to 58 months of follow-up and whose biopsy specimens (n=10) and pancreatectomies (n=10) showed rejection-related heavy or atypical inflammatory infiltrates. Features typical of rejection included most (>75%) being of mixed small and large, activated-appearing T lymphocytes, a smaller component of mature plasma cells, and variable numbers of eosinophils. Cytologically atypical cells were always a minority (< 10%). The inflammation involved the septal spaces with proportional involvement of the exocrine tissue, veins, ducts, and arteries. The inflammation was particularly targeted against the acini and was associated with acinar cell damage. Features characteristic of PTLD were nodular and expansile infiltrates, composed of a significant proportion of atypical, plasmacytoid B cells (40% to 70% of the infiltrate); Reed-Sternberg-like cells were noted in two patients. The infiltrates involved the parenchyma randomly with no apparent affinity for the acinar tissue. Extensive infiltration of the peripancreatic soft tissues was common. Arterial walls were not involved in PTLD unless there was concurrent acute vascular rejection. Features identified in both conditions were foci of necrosis and infiltration of venous walls with associated endotheliitis. Samples with concurrent PTLD and acute rejection showed combinations of these features. In situ hybridization for EBER (Epstein-Barr-encoded RNAs) was positive only in the samples from patients with PTLD. Based on the assessment of morphological differences and the selective use of relatively simple ancillary techniques, PTLD can be correctly diagnosed even in small tissue samples such as needle biopsy specimens. An early diagnosis will lead to the appropriate treatment.

Immunosuppression in pancreas transplantation: progress, problems and perspective

Through 1997, over 10,000 pancreas transplants have been performed world-wide, with 88% being simultaneous kidney-pancreas transplants (SKPTs). Current 1-year patient survival exceeds 90% and pancreas graft survival (complete insulin independence) exceeds 80% for SKPT, 70% for sequential pancreas after kidney transplant (PAKT), and 65% for pancreas transplant alone (PTA). According to Registry data, rejection accounts for 32% of graft failures in the first year after pancreas transplantation. However, improving outcomes are expected to continue with the evolution of treatment protocols. Most pancreas transplant centres employ quadruple drug immunosuppression with anti-lymphocyte induction, using either a monoclonal or polyclonal antibody agent. In recent years, there has been an overall decline in the use of antibody-induction therapy from 90% during 1987-93, to 83% of pancreas transplants performed during 1994-97. Maintenance immunosuppression is triple therapy consisting of a calcineurin inhibitor (cyclosporine or tacrolimus), corticosteroids, and an anti-metabolite such as azathioprine (AZA) or mycophenolate mofetil (MMF). Prior to 1995, nearly all pancreas transplant recipients were managed with Sandimmune. Since 1986, tacrolimus-based therapy has been used in approximately 20% of cases, and a new microemulsion formulation of cyclosporine (Neoral) has replaced Sandimmune in contemporary post-transplant immunosuppression. In addition, MMF is replacing AZA as part of the standard immunosuppressive regimen following pancreas transplantation. At present, a number of centres are conducting various trials with new drug combinations including either Neoral or tacrolimus in combination with steroids and MMF, with or without antibody-induction therapy. From 1994 to 1997, the 1-year rates of immunologic graft loss have decreased to 2% after SKPT, 9% after PAKT, and 16% after PTA. The current array of new immunosuppressive agents are providing more effective control of rejection and permitting solitary pancreas transplantation to become an accepted treatment option in diabetic patients without advanced complications. The apparent potency of new drug combinations has also resulted in a resurgence of interest in steroid withdrawal. Immunosuppressive strategies will continue to evolve to achieve effective control of rejection while minimizing 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. Pancreas transplantation will remain an important alternative in the treatment of diabetic patients until other strategies are developed that can provide equal glycaemic control with less immunosuppression and overall morbidity.

Solitary pancreas transplantation for nonuremic patients with labile insulin-dependent diabetes mellitus

BACKGROUND

Simultaneous pancreas-kidney transplantation has become a widely accepted treatment option for selected uremic patients with insulin-dependent diabetes mellitus (IDDM). Patient survival rates at 1 year exceed 90%, and rates of pancreas graft survival, 70%. However, solitary pancreas transplantation for nonuremic patients with IDDM has been controversial because of the less favorable outcome and the need for long-term immunosuppression with its associated morbidity and mortality.

METHODS

We studied the outcome of 225 solitary pancreas transplants during three immunosuppressive eras: the precyclosporine (CsA) era (n=83), the CsA era (n=118), and the tacrolimus era (n=24). Only patients with labile IDDM (e.g., hypoglycemic unawareness, insulin reactions, > or = 2 failed attempts at intensified insulin therapy for metabolic control) underwent solitary pancreas transplantation. Using univariate and multivariate analyses, we looked at patient and graft survival, the risk of surgical complications, and native kidney function during these three eras.

RESULTS

Pancreas graft survival improved significantly over time: 34% at 1 year after transplantation in the pre-CsA era, 52% in the CsA era, and 80% in the tacrolimus era (P=0.002). Pancreas graft loss due to rejection decreased from 50% at 1 year in the pre-CsA era, to 34% in the CsA era, to 9% in the tacrolimus era (P=0.008). The rate of technical failures (i.e., the risk of surgical complications) decreased from 30% in the pre-CsA era, to 14% in the CsA era, to 0% in the tacrolimus era (P=0.001). Patient survival rates at 1 year have ranged between 88% and 95% in the three eras (P=NS). Matching for at least one antigen on each HLA locus and avoiding HLA-B mismatches significantly decreased the incidence of rejection. The incidence of native kidney failure due to drug-induced toxicity decreased significantly over time, in part because only recipients with pretransplant creatinine clearance > or = 80 ml/min received transplants.

CONCLUSIONS

Solitary pancreas transplantation has become a viable alternative for nonuremic patients with labile IDDM. The risks of surgical complications and drug-induced nephrotoxicity have significantly decreased over time. Using tacrolimus as the mainstay immunosuppressant, patient and graft survival rates now no longer trail those of simultaneous pancreas-kidney transplantation.

Tacrolimus. An update of its pharmacology and clinical efficacy in the management of organ transplantation

Tacrolimus (FK 506) has been evaluated as immunosuppressive therapy in patients with a variety of solid organ and other transplants. Extensive data have now confirmed its efficacy as primary or rescue therapy in renal and hepatic transplantation. In prospective and historically controlled studies of primary therapy, tacrolimus generally demonstrated greater efficacy than the conventional formulation of cyclosporin for preventing episodes of acute rejection and allowed reduction of corticosteroid use. Chronic rejection rates were also significantly lower with tacrolimus in a large randomised liver transplantation trial. However, patient and graft survival rates were similar in both treatment groups (although numerically larger in adults with liver transplants). In children, rejection rates and corticosteroid requirements were usually lower with tacrolimus and patient and graft survival were generally similar with the 2 immunosuppressants. The finding of reduced corticosteroid requirements with tacrolimus may be of particular benefit in prepubertal children, who are still growing. A small amount of evidence has also accumulated regarding the use of tacrolimus as primary therapy in patients who have undergone bone marrow or heart and/or lung transplantation. Data are not conclusive, particularly in children, but tacrolimus appears to be useful for treating patients who have undergone these organ transplantations and may be associated with a lower incidence of obliterative bronchiolitis than cyclosporin in the latter group. Potential efficacy has also been shown in a limited number of patients with pancreas or pancreas-kidney, pancreatic islet and intestinal or multivisceral transplants, and in children who have undergone heart or heart-lung transplantation. Tacrolimus also has a use as rescue therapy in bone marrow, heart, lung and pancreatic transplantation, but data are currently insufficient for conclusions to be made. However, these results support the need for further study in these populations. Adverse effects occurring during tacrolimus therapy are generally of the type common to all immunosuppressive regimens. However, diabetes mellitus, neurotoxicity and nephrotoxicity are more common in tacrolimus than cyclosporin recipients. Hyperlipidaemia, hypertension, hirsutism and gingival hyperplasia are more common with cyclosporin. In 2 large multicentre clinical trials (US liver and European renal), tacrolimus was discontinued more frequently during the first year because of adverse events. However, the tolerability of tacrolimus appears related to dosage, improving as the dose is reduced. Tacrolimus should be considered an effective primary immunosuppressant in renal and hepatic transplantation. The drug is also a useful agent for rescue therapy in patients experiencing rejection or poor tolerability to cyclosporin. Thus, tacrolimus provides the clinician with an effective option for patients requiring immunosuppression and, with a different tolerability and efficacy profile to cyclosporin, it will better allow the tailoring of therapy to meet the needs of individual patients.

Outcome after splenic vein thrombosis in the pancreas allograft

The outcome and management of isolated splenic vein thrombosis in the pancreas transplant is unknown. We retrospectively reviewed the records of 76 simultaneous pancreas-kidney transplantations (SPK) and 56 solitary pancreas transplantations (SPT) performed at the University of Maryland from January 1995 to December 1996. A total of 24 patients were identified (9 SPK and 15 SPT recipients). All were systemically anticoagulated for a period of 6-8 weeks after diagnosis. In the SPK thrombosis group, anticoagulation resulted in 1-year graft survival that was equivalent to that of SPK controls (86.1% vs. 95.3%). In contrast, in SPT, thrombosis and subsequent anticoagulation were associated with decreased graft survival compared with SPT controls (26.8% vs. 78.3%; P<0.01). Although the outcome of splenic vein thrombosis in the absence of anticoagulation is unknown, these data suggest that (1) in SPK, anticoagulation for splenic vein thrombosis maintains graft survival, and (2) in SPT, anticoagulation does not alter the ultimate progression of splenic vein thrombosis to complete graft thrombosis.

Evaluation of pancreas transplant needle biopsy: reproducibility and revision of histologic grading system

BACKGROUND

Tissue samples for the diagnosis of pancreatic allograft rejection are now obtained routinely through the application of the percutaneous needle biopsy technique. The availability of biopsy material (89% adequate for diagnosis in our setting) presents a challenge for pathologists who are asked to provide a fast and accurate diagnosis of rejection and its severity, while at the same time being able to differentiate rejection from other causes of graft dysfunction.

METHODS

To differentiate rejection from other pathologic processes, 26 histologic features were assessed in 92 biopsies performed for confirmation of clinical diagnosis of rejection and the results were compared with 31 protocol biopsies, 12 allograft pancreatectomies with non-rejection pathology, and 30 native pancreas resections with various disease processes.

RESULTS

Based on these comparisons, a constellation of findings relating to the vascular, septal, and acinar inflammation was identified for the diagnosis of rejection. Application of these features led us to revise our scheme for grading rejection (ranging from 0-normal to V-severe rejection) to include the categories of "inflammation of undetermined significance" and "minimal rejection." The scheme was used by five pathologist to grade 20 biopsies independently of any clinical data and the interobserver level of agreement was highly significant (kappa=0.83, P<0.0001). This grading scheme was applied blindly to all (183) biopsies from 77 patients with 6-52 months of follow-up. The correlation of the highest degree of rejection on each patient and ultimate graft loss (0% for grades 0-I, 11.5% for grade II, 17.3% for grade III, 37.5% for grade IV, and 100% for grade V) was highly statistically significant (P<0.002). The fraction of grafts lost due to pure immunologic causes increased proportionally to the grade of rejection (0, 50, 66, and 100% for grades II, III, IV, and V, respectively).

CONCLUSIONS

This study provides strong support for the proposed pancreas rejection grading scheme and confirms its potential for practical use.

En bloc pancreas and kidney transplantation in a patient with limited vascular access

We report a successful en bloc pancreas and kidney transplantation on a type I diabetic patient with advanced peripheral arterial calcific disease, who had frequent life-threatening episodes of hypoglycemia. The en bloc double organ, created by joining the graft renal artery to the arterial Y graft of the pancreas, was implanted to the proximal left common iliac artery, which was the only site available for an arterial anastomosis. Under appropriate circumstances, this procedure would be an option for potential combined pancreas-kidney transplant recipients with severe calcific arterial disease.

Safe pancreas transplantation in patients with coronary artery disease

BACKGROUND

This study was conducted to determine the risk of clinically significant posttransplant cardiac events (PCEs) in a cohort of diabetic patients referred for pancreas transplantation.

METHODS

Between April 1991 and December 1995, 316 insulin-dependent diabetics were evaluated for pancreas transplantation. Patients were assessed for risk factors for coronary artery disease (CAD), and underwent screening for significant CAD by a standardized algorithm that included selective coronary angiography. For the 3-year period following transplantation, PCEs were identified, and related to pretransplant cardiac risk factors.

RESULTS

Only four patients (1.3%) were turned down for cardiac contraindications. Coronary angiography was done in 74 patients (27% of the active transplant candidates) during the evaluation period because of the patient's history or a positive stress test. Significant coronary artery stenoses were found in 54% of the patients catheterized. Twenty-five of these 40 patients (63%) underwent revascularization with percutaneous transluminal coronary angioplasty and/or coronary artery bypass grafting. A total of 359 organs were subsequently transplanted into 194 of these patients. No deaths occurred within 30 days of any of the transplants; four percent of transplant recipients died of cardiac causes within the follow-up period (median 23 months). Those with no pretransplant evidence of CAD had significantly lower rates of PCE (2% and 8% at 1 and 3 years, respectively) than those with pretransplant evidence of CAD (11% and 29% at 1 and 3 years, P<0.01; relative risk, 4.3).

CONCLUSIONS

Routine cardiac screening of pancreas recipients with selective angiography and revascularization allows patients with significant CAD to safely undergo pancreas transplantation. Patients should rarely be excluded from pancreas transplantation for cardiac causes.

Post-transplant diabetes mellitus. The role of immunosuppression

Immunosuppressive agents increase the risk of death due to coronary disease or stroke by their ability to cause 3 different adverse effects: dyslipidaemia, hypertension and hyperglycaemia. Post-transplant diabetes mellitus has emerged as a major adverse effect of immunosuppressants. As recipients of organ transplants survive longer, the secondary complications of diabetes mellitus have assumed greater importance. There is a need for a precise definition of post-transplant diabetes mellitus to facilitate inter-centre comparison and to study the natural history of post-transplant diabetes mellitus. We recommend broad criteria to define hyperglycaemia, as a fasting blood glucose level of > 400 mg/dl at any point or > 200 mg/dl for 2 weeks, or a need for insulin treatment for at least 2 weeks. We also recommend serial measurements of HbA1c. Cyclosporin and tacrolimus cause post-transplant diabetes mellitus by a number of mechanisms, including decreased insulin secretion, increased insulin resistance or a direct toxic effect on the beta cell. For corticosteroids, the induction of insulin resistance seems to be the predominant factor. However, few studies have examined the mechanism of diabetogenicity at the molecular level. This may hold the key for pharmacological manipulation of current immunosuppressive regimens which may result in decreased metabolic complications. Corticosteroid sparing regimens have been shown to reduce the metabolic complications of immunosuppressants including post-transplant diabetes mellitus. However, their use should be balanced against the increased incidence of transplant rejections. Post-transplant diabetes mellitus may be organ-specific irrespective of the immunosuppressant used. Tacrolimus causes a high incidence of post-transplant diabetes mellitus in recipients of kidney transplants (upto 20% in some reports); the diabetogenicity of cyclosporin-based regimens is comparable with that of tacrolimus-based regimens in recipients of liver transplants. A few clinical studies in which attempts were made to discontinue cyclosporin resulted in an unacceptable loss of the transplant. In the case of tacrolimus, complete withdrawal of immunosuppression may be possible in selected patients with liver transplants. However, post-transplant recipients who may benefit from this approach are difficult to identify. In some early series, patients received doses of tacrolimus that were approximately 2 to 3 times higher than those currently used, which may have resulted in a higher incidence of post-transplant diabetes mellitus. More recently, it has been shown that tacrolimus was successful in salvaging whole pancreatic grafts which were maintained on cyclosporin. Tacrolimus-based immunosuppression as primary therapy was also used with remarkable success in solitary whole pancreas transplants. Strategies to reduce the metabolic complications of immunosuppressants should be pursued aggressively as this will directly lead to a decrease in long term cardiovascular adverse effects.