Long-term outcomes in pediatric liver recipients: comparison between cyclosporin A and tacrolimus

Incidence and risk factors for chronic rejection in pediatric liver transplantation

Chronic rejection (CR) is a progressive immunological injury that frequently leads to long-term liver allograft dysfunction and loss. Although CR remains an important indication for retransplantation, as transplant immunosuppression has evolved, its prevalence in adults undergoing liver transplantation (LT) has declined. However, the incidence and factors that lead to CR in pediatric LT are poorly defined. Therefore, we sought to systematically measure CR's incidence and assess both the risk factors for developing CR and outcomes in a large cohort of pediatric recipients of LT. In this single-center study, we retrospectively analyzed and compared relevant recipient characteristics, surgical details, immunosuppression, graft, and patient survival in the CR and control groups over a 17-year period. After a median time of 1.9 years after LT, 19/356 recipients of LT (5.3%) developed CR in our cohort. Posttransplant lymphoproliferative disorder ( p = 0.01), infections ( p = 0.02), autoimmune liver diseases (HR = 7.3, p = <0.01), Black race (HR = 11.5, p = 0.01), and 2 or more episodes of T cell mediated rejection (HR = 5.1, p = <0.01) were associated with CR development. The retransplantation rate among CR cases was 15.8% at a median follow-up time of 4.1 years. Overall, patient survival was lower in the CR group (78.9%) versus controls (91.1%). While CR incidence in our pediatric cohort was lower than previously reported rates of >12%, the CR group had a higher graft failure rate that required retransplantation and lower overall patient survival. Thus, identifying risk factors may warrant specialized immunosuppression protocols and closer posttransplantation monitoring to reduce the risk of morbidity and mortality from CR.

Post-transplant lymphoproliferative disorder associated Epstein-Barr virus DNAemia after liver transplantation in children: Experience from single center

The most prevalent malignancy that complicates both adult and pediatric solid organ transplantation is post-transplant lymphoproliferative disorder (PTLD). This study aimed to analyze the clinical and pathological characteristics, treatments, and outcomes of Epstein-Barr virus (EBV) DNAemia and PTLD in pediatric liver transplant recipients. A retrospective chart review was performed on 112 patients less than 18 years of age who underwent isolated orthotopic liver transplantation (OLT) between 2010 and 2022 at Ege University Children's Hospital. Data gathered for 1-year post-OLT included age at OLT, EBV, immunoglobulin (Ig)M/IgG status of the donor and recipient, indication for OLT, induction regimen, all immunosuppression levels, date and result of EBV polymerase chain reaction testing, rejection episodes documented by liver biopsy, and the development of PTLD. Forty-nine patients (43.75%) developed EBV DNAemia (median interval from surgery: 2 months, min-max: 2-36), of which 43 (87.8%) grafts came from living donors, and 6 (12.2%) came from deceased donors. Nine (18.4%) patients died during follow-up, and eight (16.3%) developed PTLD. Of these 8 patients; five patients developed EBV-related disease, one child developed hemophagocytic lymphohistiocytosis, one developed aplastic anemia, and one child developed B cell lymphoma. When PTLD patients and without-PTLD patients were compared, pediatric intensive care unit hospitalization, abnormal bone marrow biopsy findings, lymphadenopathy, age at diagnosis of EBV DNAemia, EBV viral load, tacrolimus (FK 506) pre-infection, were higher and tacrolimus 1-month levels were lower in patients with PTLD (p < 0.05). In logistic regression analysis, we showed that the age at diagnosis of EBV DNAemia was significantly higher in children with PTLD (p = 0.045; OR: 1.389; 95% CI: 1.007-1.914). PTLD is a rare but severe complication associated with EBV after OLT. This study demonstrated that PTLD is associated with older age, higher tacrolimus blood levels before EBV DNAemia, and higher peak EBV viral load at 1 month of EBV DNAemia.

Post Transplant Lymphoproliferative Disorder

Posttransplant lymphoproliferative disorder is an extremely fatal complication arising in transplant recipients as a side effect of immunosuppression. PTLDs are seen after both solid organ and hematopoietic stem cell transplants though the incidence is much higher in the former. Primary Epstein-Barr virus (EBV) infection or reactivation due to a state of immune dysregulation along with intensity of immunosuppression used are of paramount importance in pathogenesis of PTLD. EBV associated PTLDs occur early in the post transplant period whereas late onset lymphomas are usually EBV negative. The uncontrolled B cell proliferation can create a spectrum of histological patterns from nondestructive lesions to destructive polymorphic or more aggressive monomorphic PTLDs. Early detection of seropositivity by serial monitoring in the recipient can prevent PTLD development by starting pre-emptive therapy. The mainstay treatment in established cases remains reduction of immunosuppression. Chemotherapeutic and immunomodulatory agents are added sequentially based on the type of PTLD and based on its response to initial therapy. Despite various treatment options available, the morbidity remains high and achieving state of disease remission without causing graft rejection can be quite challenging. Hence, a better understanding in pathobiology of EBV+ versus EBV- PTLDS may help prevent lymphomagenesis in transplant recipients.

Efficacy and safety of tacrolimus in de novo pediatric transplant recipients randomized to receive immediate- or prolonged-release tacrolimus

BACKGROUND AND AIMS

This multicenter trial compared immediate-release tacrolimus (IR-T) vs prolonged-release tacrolimus (PR-T) in de novo kidney, liver, and heart transplant recipients aged <16 years. Each formulation had similar pharmacokinetic (PK) profiles. Follow-up efficacy and safety results are reported herein.

MATERIALS AND METHODS

Patients, randomized 1:1, received once-daily, PR-T or twice-daily, IR-T within 4 days of surgery. After a 4-week PK assessment, patients continued randomized treatment for 48 additional weeks. At Year 1, efficacy assessments included the number of clinical acute rejections, biopsy-confirmed acute rejection (BCAR) episodes (including severity), patient and graft survival, and efficacy failure (composite of death, graft loss, BCAR, or unknown outcome). Adverse events were assessed throughout.

RESULTS

The study included 44 children. At Year 1, mean ± standard deviation tacrolimus trough levels were 6.6 ± 2.2 and 5.4 ± 1.6 ng/mL, and there were 2 and 7 acute rejection episodes in the PR-T and IR-T groups, respectively. No cases of graft loss or death were reported during the study. The overall efficacy failure rate was 18.2% (PR-T n = 1; IR-T n = 7).

CONCLUSIONS

In pediatric de novo solid organ recipients, the low incidence of BCAR and low efficacy failure rate suggest that PR-T-based immunosuppression is effective and well tolerated to 1-year post-transplantation.

International Liver Transplantation Society Consensus Statement on Immunosuppression in Liver Transplant Recipients

Effective immunosupression management is central to achieving optimal outcomes in liver transplant recipients. Current immunosuppression regimens and agents are highly effective in minimizing graft loss due to acute and chronic rejection but can also produce a substantial array of toxicities. The utilization of immunosuppression varies widely, contributing to the wide disparities in posttransplant outcomes reported between transplant centers. The International Liver Transplantation Society (ILTS) convened a consensus conference, comprised of a global panel of expert hepatologists, transplant surgeons, nephrologists, and pharmacologists to review the literature and experience pertaining to immunosuppression management to develop guidelines on key aspects of immunosuppression. The consensus findings and recommendations of the ILTS Consensus guidelines on immunosuppression in liver transplant recipients are presented in this article.

Side effects and efficacy of renal sparing immunosuppression in pediatric liver transplantation-A single center matched cohort study

Immunosuppressive combination therapy with MMF can reduce CNI associated nephrotoxicity. We investigated effectiveness and safety of de novo MMF-tacrolimus based immunosuppression after pLTx. Patients after pLTx receiving immunosuppression with MMF/tacrolimus (MMF/TAC) were compared to retrospectively selected age- and diagnosis-matched patients with tacrolimus monotherapy (TAC) and cyclosporine/prednisolone therapy (CSA) (19 patients each, n = 57). Effectiveness, renal function and side effects were analyzed for 1 year after pLTx. Tacrolimus reduction in combination therapy (0.7 μg/L over the year) was lower than aspired (2 μg/L). Acute BPAR occurred equally in MMF/TAC and TAC groups (31.6% each), being slightly higher in CSA group (42.1%; OR = 1.5; 95% CI = 0.42-5.44; P = .5). GFR deteriorated comparably in all 3 groups (P < .01 each) without significant differences between the groups. Septicemia was detected significantly more often in MMF/TAC (73.6%) than in TAC (31.6%) (OR 4.17; 1.07-16.27; P = .04). EBV reactivation occurred more often in CSA patients (84.2%) than in MMF/TAC (47.4%; OR 5.16; 0.98-27.19; P = .05) and TAC patients (52.6%; OR 8.16; 1.48-44.89; P = .02) the same was true for other viral infections (47.4% (CSA) vs 15.8% (TAC); OR 4.21; 0.95-18.55; P = .05). Our study does not provide additional evidence for a benefit of initial use of MMF/TAC over TAC regarding renal function, but raises concerns regarding a potentially increased risk of serious infections under MMF/TAC compared to TAC monotherapy at equivalent renal outcome; our study is, however, limited by the minor CNI reduction in combination therapy.

Living donor liver transplantation during the first 3 months of life

Living donor liver transplantation (LDLT) is now an established technique for treating children with end-stage liver disease. Few data exist about liver transplantation (LT) for exclusively young infants, especially infants of <3 months of age. We report our single-center experience with 12 patients in which LDLT was performed during the first 3 months of life and compare the results with those of older infants who underwent LT. All of the patients were treated at the National Center of Child Health and Development, Tokyo, Japan. Between November 2005 to November 2016, 436 children underwent LT. Twelve of these patients underwent LT in the first 3 months of life (median age, 41 days; median weight, 4.0 kg). The indications for transplantation were fulminant hepatic failure (n = 11) and metabolic liver disease (n = 1). All the patients received the left lateral segment (LLS) in situ to mitigate the problem of graft-to-recipient size discrepancy. A reduced LLS graft was used in 11 patients and a segment 2 monosegment graft was used in 1 patient. We compared the results with those of infants who were 4-6 months of age (n = 67) and 7-12 months of age (n = 110) who were treated in the same study period. There were significant differences in the Pediatric End-Stage Liver Disease score and the conversion rate of tacrolimus to cyclosporine in younger infants. Furthermore, the incidence of biliary complications, bloodstream infection, and cytomegalovirus infection tended to be higher, whereas the incidence of acute cellular rejection tended to be lower in younger infants. The overall cumulative 10-year patient and graft survival rates in recipients of <3 months of age were both 90.9%. LDLT during the first 3 months of life appears to be a feasible option with excellent patient and graft survival. Liver Transplantation 23 1051-1057 2017 AASLD.

Matched-pair analysis: identification of factors with independent influence on the development of PTLD after kidney or liver transplantation

BACKGROUND

Post-transplant lymphoproliferative disorder (PTLD) adversely affects patients' long-term outcome.

METHODS

The paired t test and McNemar's test were applied in a retrospective 1:1 matched-pair analysis including 36 patients with PTLD and 36 patients without PTLD after kidney or liver transplantation. Matching criteria were age, gender, indication, type of transplantation, and duration of follow-up. All investigated PTLD specimen were histologically positive for EBV. Risk-adjusted multivariable regression analysis was used to identify independence of risk factors for PTLD detected in matched-pair analysis. The resultant prognostic model was assessed with ROC-curve analysis.

RESULTS

Patients suffering with PTLD had shorter mean survival (p = 0.004), more episodes of CMV infections or reactivations (p = 0.042), and fewer recipient HLA A2 haplotypes (p = 0.007), a tacrolimus-based immunosuppressive regimen (p = 0.052) and higher dosages of tacrolimus at hospital discharge (Tac dosage) (p = 0.052). Significant independent risk factors for PTLD were recipient HLA A2 (OR = 0.07, 95 % CI = 0.01-0.55, p = 0.011), higher Tac dosages (OR = 1.29, 95 % CI = 1.01-1.64, p = 0.040), and higher numbers of graft rejection episodes (OR = 0.38, 95 % CI = 0.17-0.87, p = 0.023). The following prognostic model for the prediction of PTLD demonstrated good model fit and a large area under the ROC curve (0.823): PTLD probability in % = Exp(y)/(1 + Exp(y)) with y = 0.671 - 1.096 × HLA A2-positive recipient + 0.151 × Tac dosage - 0.805 × number of graft rejection episodes.

CONCLUSIONS

This study suggests prognostic relevance for recipient HLA A2, CMV, and EBV infections or reactivations and strong initial tacrolimus-based immunosuppression. Patients with risk factors may benefit from intensified screening for PTLD.

Prognostic factors for the evolution and reversibility of chronic rejection in pediatric liver transplantation

OBJECTIVE

Chronic rejection remains a major cause of graft failure with indication for re-transplantation. The incidence of chronic rejection remains high in the pediatric population. Although several risk factors have been implicated in adults, the prognostic factors for the evolution and reversibility of chronic rejection in pediatric liver transplantation are not known. Hence, the current study aimed to determine the factors involved in the progression or reversibility of pediatric chronic rejection by evaluating a series of chronic rejection cases following liver transplantation.

METHODS

Chronic rejection cases were identified by performing liver biopsies on patients based on clinical suspicion. Treatment included maintaining high levels of tacrolimus and the introduction of mofetil mycophenolate. The children were divided into 2 groups: those with favorable outcomes and those with adverse outcomes. Multivariate analysis was performed to identify potential risk factors in these groups.

RESULTS

Among 537 children subjected to liver transplantation, chronic rejection occurred in 29 patients (5.4%). In 10 patients (10/29, 34.5%), remission of chronic rejection was achieved with immunosuppression (favorable outcomes group). In the remaining 19 patients (19/29, 65.5%), rejection could not be controlled (adverse outcomes group) and resulted in re-transplantation (7 patients, 24.1%) or death (12 patients, 41.4%). Statistical analysis showed that the presence of ductopenia was associated with worse outcomes (risk ratio=2.08, p=0.01).

CONCLUSION

The presence of ductopenia is associated with poor prognosis in pediatric patients with chronic graft rejection.

Extended follow-up of pediatric liver transplantation patients receiving once daily calcineurin inhibitor

We describe longitudinal results in a cohort of pediatric liver transplant patients successfully minimized to once daily CNI monotherapy for longer than five yr and assess changes in liver biochemistries and liver histology. A retrospective chart review of all pediatric liver transplant patients at a single center was performed. Biopsies and serum biochemistries (AST, ALT, total bilirubin, direct bilirubin, INR, creatinine) are reported at time points: PM, five-yr, seven-yr, and nine-yr post-minimization. Biopsies were assessed for inflammation and fibrosis using Ishak and Batts grading systems. Successful minimization to daily CNI monotherapy was defined as normal liver enzymes with no episodes of rejection. Thirty-three patients have successfully remained on once daily CNI for >5 yr, and 19/33 of these patients have serial liver biopsies available for review. We report on the clinical and histological findings of these 19 patients. All 19 patients continue to have normal liver biochemistries. On post-minimization biopsies, fibrosis progressed by ≥2 stages in one patient (5.3%) despite normal liver biochemistries. Carefully selected patients can tolerate minimization to once daily CNI monotherapy as few have progression of fibrosis.

The Impact of EBV Status on Characteristics and Outcomes of Posttransplantation Lymphoproliferative Disorder

We examined the associations of Epstein-Barr virus (EBV) status with characteristics and outcomes of posttransplantation lymphoproliferative disorder (PTLD) by studying 176 adult solid organ transplant recipients diagnosed with PTLD between 1990 and 2013 (58 [33%] EBV-negative; 118 [67%] EBV-positive). The proportion of EBV-negative cases increased over time from 10% (1990-1995) to 48% (2008-2013) (p < 0.001). EBV-negative PTLD had distinct characteristics (monomorphic histology, longer latency) though high-risk features (advanced stage, older age, high lactate dehydrogenase, central nervous system involvement) were not more common compared to EBV-positive PTLD. In multivariable analysis, EBV negativity was not significantly associated with worse response to initial therapy (adjusted odds ratio, 0.84; p = 0.75). The likelihood of achieving a complete remission (CR) was not significantly different for EBV-negative versus EBV-positive PTLD including when therapy was reduction of immunosuppression alone (35% vs. 43%, respectively, p = 0.60) or rituximab (43% vs. 47%, p = 1.0). EBV negativity was also not associated with worse overall survival (adjusted hazard ratio, 0.91; p = 0.71). Our findings indicate that EBV status is not prognostic or predictive of treatment response in adults with PTLD. The high proportion of EBV-negative disease diagnosed in recent years highlights the need for new strategies for prevention and management of EBV-negative PTLD.

Severe post-transplant lymphoproliferative disorder after living donor liver transplantation

Post-transplant lymphoproliferative disorder (PTLD) is a well-known complication after transplantation. A living donor liver transplantation was performed on a 31-year-old man for fulminant hepatitis. He again developed liver dysfunction after 7 months. He was diagnosed as having acute cellular rejection and the steroid pulse therapy introduced resulted in little improvement. He gradually developed a high fever and right axillary lymphadenopathy appeared. Chest computed tomography (CT) was performed revealing small lung nodules and axillary lymphadenopathy. Because his serological status for Epstein-Barr virus was positive, PTLD was highly suspected and immunosuppression treatment was withdrawn with little improvement. One week later, he developed tachycardia. Chest CT was re-performed revealing an infiltration to the left cardiac chamber. For diagnosis, axillary lymph node biopsy was performed and during the procedure, he developed ventricular tachycardia (VT). Immunohistological staining revealed PTLD of T lymphocytes, and chemotherapy was introduced on the same day he developed VT. After two cycles of tetrahydropyranyl, adriamycin, cyclophosphamide, vincristine, prednisolone and etoposide treatment, he completely recovered. This is a first case report of severe PTLD with VT, and our case implies the feasibility of chemotherapy after the appearance of dissemination symptoms.

Decreasing incidence of symptomatic Epstein-Barr virus disease and posttransplant lymphoproliferative disorder in pediatric liver transplant recipients: report of the studies of pediatric liver transplantation experience

Posttransplant lymphoproliferative disorder (PTLD) causes significant morbidity and mortality in pediatric recipients of liver transplantation (LT).

OBJECTIVE

Describe the incidence of PTLD and symptomatic Epstein-Barr virus (SEBV) disease in a large multicenter cohort of children who underwent LT with a focus on the risk factors and changes in incidence over time. SEBV and PTLD were prospectively determined in 2283 subjects who had undergone LT for the first time with at least 1 year of follow-up in the Studies of Pediatric Liver Transplantation database. SEBV was defined with specific criteria, and PTLD required tissue confirmation. The incidence of SEBV and PTLD was determined with a Kaplan-Meier analysis. Univariate and multivariate modeling of risk factors was performed with standard methods. SEBV occurred in 199 patients; 174 (87.4%) were EBV-negative at LT. Seventy-five patients developed PTLD, and 64 (85.3%) of these patients were EBV-negative at LT. Among the 2048 patients with at least 2 years of follow-up, 8.3% developed SEBV by the second year after LT, and 2.8% developed PTLD. There were lower rates of SEBV (5.9% versus 11.3%, P < 0.001) and PTLD (1.7% versus 4.2%, P = 0.001) in 2002-2007 versus 1995-2001. In 2002-2007, tacrolimus and cyclosporine trough blood levels in the first year after LT were significantly lower, and fewer children were receiving steroids. Biliary atresia, and recipient EBV status were correlated. In a multivariate analysis, era of LT, recipient EBV status, and frequent rejection episodes were associated with SEBV and PTLD. The incidence of SEBV and PTLD is decreasing in pediatric LT recipients concomitantly with a reduction in immunosuppression. Younger recipients and those with multiple rejections remain at higher risk for SEBV and PTLD.

Posttransplant Lymphoproliferative Disorder after Cardiac Transplantation in Children: Life Threatening Complications Associated with Chemotherapy Combined with Rituximab

Despite the excellent long-term survival currently achieved in pediatric heart transplant recipients, posttransplant lymphoproliferative disorders (PTLDs) are one of the most important causes of morbidity and mortality after heart transplantation (HTx), especially in children. Timely and accurate diagnosis based on histological examination of biopsy tissue is essential for early intervention for PTLD. Chemotherapy is indicated for patients with poor response to reduction of immunosuppressive medication and for highly aggressive monomorphic PTLD. The use of rituximab in combination with chemotherapy is effective to suppress B cell type PTLD (B-PTLD). However, PTLD relapses frequently and the outcome is still poor. Although everolimus (EVL) has been reported to inhibit growth of human Epstein-Barr-virus- (EBV-) transformed B lymphocytes in vitro and in vivo, EVL has several side effects, such as delayed wound healing and an increase in bacterial infection. During combined treatment of chemotherapy and rituximab, B-PTLDs are sometimes associated with life-threatening complications, such as intestinal perforation and cardiogenic shock due to cytokine release syndrome. In HTx children especially treated with EVL, stoma should be made to avoid reoperation or sepsis in case of intestinal perforation. In cases with cardiac graft dysfunction possibly due to cytokine release syndrome by chemotherapy with rituximab for PTLD, plasma exchange is effective to restore cardiac function and to rescue the patients.

Immunosuppressive and immunomodulatory therapy-associated lymphoproliferative disorders

A variety of therapeutic agents may increase the risk of lymphoproliferative disorders/neoplasms. These include those agents used to treat other malignancies (i.e., cytotoxic chemotherapy) and those used to treat or prevent certain diseases (or graft rejection) that alter the immune system. This review is restricted to the secondary lymphoid disorders that are unrelated to primary DNA damage by cytotoxic chemotherapy, and thus will include discussions regarding post-transplant lymphoproliferative disorders and those lymphoproliferations associated with the therapy of autoimmune and other immune-mediated diseases. Three drugs, or classes of drugs, used in the treatment of autoimmune and other immune-mediated diseases are discussed in some detail. These include methotrexate, anti-metabolites (including thiopurines and mycophenolate mofetil), and immunomodulators. The appropriate recognition of these disorders is important in order to correctly classify and institute appropriate therapy, recognizing that reduced immunosuppression or withdrawal of therapy may be necessary, rather than treating as a malignant lymphoma.

Managing post-transplant lymphoproliferative disorders in solid-organ transplant recipients: a review of immunosuppressant regimens

Post-transplant lymphoproliferative disorders (PTLD) are a heterogeneous group of potentially life-threatening complications that occur after solid organ and bone marrow transplantation. Risk factors for acquiring PTLD are type of organ transplanted, age, intensity of immunosuppression, viral infections such as Epstein-Barr virus (EBV) and time after transplantation. Due to a dearth of well designed prospective trials, treatment for PTLD is often empirical, with reduction in immunosuppression accepted as the first step. Rituximab, a monoclonal antibody directed against the CD20 antigen of immature B cells, is often used as monotherapy after reduction in immunosuppression, although this is associated with a high risk of relapse if patients have at least one of the following risk factors: age greater than 60 years, elevated lactate dehydrogenase levels and Eastern Cooperative Oncology Group Score between 2 and 4. For such patients, rituximab should be considered in combination with CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone), particularly if high-grade PTLD is present. Although widely prescribed, the use of ganciclovir for PTLD remains controversial as EBV-transformed cells lack the thymidine kinase necessary for ganciclovir activation. Newer antivirals that combine ganciclovir with activators of cellular thymidine kinase have shown promising results in preclinical studies. In the absence of controlled trials, surgery may be indicated for localized disease and radiotherapy for patients with impending spinal cord compression or disease localized to the central nervous system or orbit. Future interventions may include adoptive immunotherapy, intravenous immunoglobulin, mammalian target of rapamycin inhibitors, monoclonal antibodies to interleukin-6 and galectin-1, and even EBV vaccination. Although several trials are in progress, it is necessary to wait for the long-term outcome of these studies on risk of PTLD relapse.

Lymphoproliferative disorders after solid organ transplantation-classification, incidence, risk factors, early detection and treatment options

Posttransplant lymphoproliferative disorder (PTLD) is a heterogeneous disease group of benign and malignant entities. The new World Health Organisation classification introduced in 2008 distinguishes early lesions, polymorphic, monomorphic and classical Hodgkin lymphoma-type PTLD. Based on the time of appearance, early and late forms can be identified.PTLDs are the second most frequent posttransplantation tumors in adulthood, and the most frequent ones in childhood. The incidence varies with the transplanted organ-from 1%-2% following kidney transplantation to as high as 10% following thoracic organ transplantation-due to different intensities in immunosuppression. Immunocompromised state and Epstein-Barr virus (EBV) infection are the two major risk factors.In Europe and the US approximately 85% of PTLDs are of B-cell origin, and the majority are EBV-associated. Symptoms are often unspecific; extranodal, organ manifestations and central nervous system involvement is common. Early lesions respond well to a decrease in immunosuppression. Malignant entities are treated with rituximab, chemotherapy, radiotherapy and surgical therapy. Adoptive T-cell transfer represents a promising therapeutic approach. The prognosis is favorable in early PTLD, and poor in late PTLD. Five-year survival is 30% for high-grade lymphomas. The prognosis of EBV-negative lymphomas is worse.Lowering the risk of PTLD may be achieved by low dose maintenance immunosuppression, immunosuppressive drugs inhibiting cell proliferation, and special immunotherapy (e.g. interleukin-2 inhibitors). Early detection is especially important for high risk-e.g. EBV-negative-patients, where the appearance of EBV-DNA and the increase in its titer may help.

Long term management of liver transplant rejection in children

The current management of hepatic allograft rejection after liver transplantation in children requires effective baseline immunosuppression to prevent rejection and rapid diagnosis and treatment to manage acute rejection episodes. The subsequent impact on chronic rejection is dependent on the combination of adequate prevention and the treatment of acute rejection. Tacrolimus is a macrolide lactone that inhibits the signal transduction of interleukin-2 (IL-2) via calcineurin inhibition. Introduced in 1989, tacrolimus was first used in the salvage of refractory acute or chronic rejection under cyclosporin or to rescue patients with significant cyclosporin-related complications. The majority of paediatric transplant centres use a combination of steroids with tacrolimus as a basic immunosuppressant regimen following paediatric liver transplantation. This combination has allowed the acute cellular rejection-free rate to increase to between 30 and 60%, while lowering the rate of refractory rejection to less than 5%. Corticosteroid-resistant rejection is commonly treated with monoclonal (muromonab CD3) or polyclonal preparations. Although most episodes of acute cellular rejection occur during the first 6 weeks after liver transplant, the appearance of late acute liver allograft rejection must raise the question of noncompliance, especially in the adolescent population. Chronic rejection is becoming increasingly rare under tacrolimus-based immunosuppression. Tacrolimus is effective in reversing refractory acute cellular rejection or early chronic rejection in patients initially treated with cyclosporin-based regimens. Patients with a history of noncompliance as well as children with autoimmune liver disease are at risk of chronic rejection. Retransplantation therapy for chronic rejection has, fortunately, become more rare in the tacrolimus era with only 3% of retransplants being performed for this indication. Newer immunosuppressive agents are further modifying the long term management of liver allograft rejection. These include mycophenolate mofetil, rapamycin and IL-2 antibodies such as daclizumab. The development of these agents is allowing patient-specific immunosuppressive management to minimise rejection as well as the complications related to immunosuppression.

Diagnosis of post-transplant lymphoproliferative disorder in solid organ transplant recipients - BCSH and BTS Guidelines

A joint working group established by the Haemato-oncology subgroup of the British Committee for Standards in Haematology (BCSH) and the British Transplantation Society (BTS) has reviewed the available literature and made recommendations for the diagnosis and management of post-transplant lymphoproliferative disorder (PTLD) in adult recipients of solid organ transplants. This review details the risk factors predisposing to development, initial features and diagnosis. It is important that the risk of developing PTLD is considered when using post transplant immunosuppression and that the appropriate investigations are carried out when there are suspicions of the diagnosis. These must include tissue for histology and computed tomography scan to assess the extent of disease. These recommendations have been made primarily for adult patients, there have been some comments made with regard to paediatric practice.

Towards minimizing immunosuppression in pediatric liver transplant recipients

Immunosuppression regimens after liver transplantation focus mainly on preventing rejection and subsequent graft loss. However, in children, morbidity and mortality rates from infections exceed those from rejection after transplant, and immunosuppression can hinder growth, renal function, and graft tolerance. We hypothesized that early steroid withdrawal, with a primary aim of TAC monotherapy would yield no penalty in terms of rejection and graft loss, while reducing risks of infection and maximizing growth. We prospectively evaluated 64 consecutive pediatric liver transplant recipients. One yr patient/graft survival was 93/90%, respectively. At one yr post-transplant, 75.4% of patients were on TAC monotherapy. No deaths or graft losses were caused by infection. Sixty-one percent of patients had at least one episode of rejection, most within three months following transplant and 3.8% were treated for chronic rejection. One non-compliant adolescent died from chronic rejection. CMV, EBV, and lymphoproliferative disease rates were 3.1%, 5.3%, 1.8%, respectively. Pretransplant and one yr post-transplant glomerular filtration rates were unchanged. One yr improved catch-up growth was observed. We conclude that immunosuppression minimization after pediatric liver transplant yields no serious complications from rejection, and might confer advantages with respect to infection, renal function, growth, and is deserving of wider application and study.

Long-term management of immunosuppression after pediatric liver transplantation: is minimization or withdrawal desirable or possible or both?

PURPOSE OF REVIEW

The aim is to review available data regarding the risks and benefits of indefinite immunosuppression against attempted immunosuppression withdrawal for children who have undergone liver transplantation.

RECENT FINDINGS

Emerging data suggest that conventional immunosuppression practices may well be responsible for a substantial proportion of the long-term mortality and morbidity burden borne by pediatric liver transplant recipients. The cumulative risk of chronic kidney disease, infection, malignancy, and cardiovascular risk factors such as hypertension, diabetes, and hyperlipidemia appear to threaten the health and well being of children more than that of acute or chronic allograft rejection. In parallel, single-center experiences have suggested that gradual immunosuppression withdrawal can be done safely with higher success rates in pediatric compared with adult liver transplant recipients. The coalescence of these two data streams has engendered substantial interest in systematic exploration of the safety and efficacy of immunosuppression withdrawal in conjunction with a vigorous scientific effort to elucidate an immunologic signature predictive of successful withdrawal.

SUMMARY

There is a concerted effort within the transplant community to identify biomarkers that can accurately predict the success of immunosuppression withdrawal after liver transplantation. Freedom from lifelong immunosuppression is likely to yield considerable benefit, particularly for children who face the longest lifetime horizons.

Long-term outcome of mycophenolate mofetil rescue therapy for resistant acute allograft rejection in pediatric liver transplant recipients

Mycophenolate mofetil (MMF) has been used to rescue liver allografts with steroid-resistant rejection (SRR). However, the long-term outcome of these patients is not known. This study evaluates the long-term outcome of MMF rescue therapy for SRR in pediatric liver allograft recipients. Twenty-six children (who received 28 liver transplants), including 16 girls, were given MMF for SRR. The median age at transplant was 1.7 (range 0.4-13.6) years. Primary immunosuppression was cyclosporine-based in 22 and tacrolimus-based in 6. All patients except one had been converted to tacrolimus prior to MMF, having already received a median of 2 (1-5) courses of high-dose intravenous methylprednisolone. The median time to MMF rescue therapy was 1.8 (0.4-35.8) months. Twenty-one of 28 episodes of SRR responded to MMF therapy. The median follow-up was 8.8 (7.7-11.5) years. In responders, there was 1 death from posttransplant lymphoproliferative disease, and no grafts were lost to chronic rejection. In the 7 nonresponders, 3 grafts were lost to chronic rejection with 2 patient deaths. Surviving children are clinically well with good liver function, and 17 remain on MMF. Three children have glomerular filtration < 80 mL/minute/1.73 m(2). Side effects of MMF were seen in 12 patients; diarrhea (n = 5) and leukopenia (n = 5) being the most common. MMF was found to be effective in treating SRR in pediatric allograft recipients, with good long-term graft function and an acceptable side-effect profile.

Late graft loss or death in pediatric liver transplantation: an analysis of the SPLIT database

Late graft loss (LGL) and late mortality (LM) following liver transplantation (LT) in children were analyzed from the studies of pediatric liver transplantation (SPLIT) database. Univariate and multivariate associations between pre- and postoperative factors and LGL and LM in 872 patients alive with their primary allografts 1 year after LT were reviewed. Thirty-four patients subsequently died (LM) and 35 patients underwent re-LT (LGL). Patients who survive the first posttransplant year had 5-year patient and graft survival rates of 94.2% and 89.2%, respectively. Graft loss after the first year was caused by rejection in 49% of the cases with sequelae of technical complications accounting for an additional 20% of LGL. LT for tumor, steroid resistant rejection, reoperation in the first 30 days and >5 admissions during the first posttransplant year were independently associated with LGL in multivariate analysis. Malignancy, infection, multiple system organ failure and posttransplant lymphoproliferative disease accounted for 61.8% of all late deaths after LT. LT performed for FHF and tumor were associated with LM. Patients who are at or below the mean for weight at the time of transplant were also at an increased risk of dying. Frequent readmission was also found to be associated with LM.

Outcomes of primary liver cancer in children: an appraisal of experience

INTRODUCTION

Hepatoblastoma (HB) and hepatocellular carcinoma (HCC) are the most common primary liver cancers in children. Recent advances in management of pediatric liver cancer have improved disease-specific survival (DSS). This is a review of our experience with childhood liver malignancy over the past 3 decades.

MATERIALS AND METHODS

A retrospective chart review from 1975 to 2005 identified patients who were 18 years old or younger with a histologically confirmed diagnosis of primary liver cancer. Patients were staged according to the Children's Cancer Group and Pediatric Oncology Group (CCG/POG) system. Patients were followed up prospectively through clinic visits and mail correspondence. Standard statistical methods were used for comparison, risk, and survival analyses.

RESULTS

Fifty-two patients were confirmed to have primary liver cancers, where 24 (46%) patients had HB, 22 (42%) had HCC, 3 (6%) had sarcomas, and 3 (6%) had other histologies. Mean ages at presentation for HB and HCC were 3.2 and 13.1 years old, respectively. The most common presentations were abdominal mass (67%) and pain (40%). Most patients underwent major liver resection (n = 45, 87%), including: lobectomy (n = 25, 48%), and trisegmentectomy (n = 11, 21%). Three patients underwent liver transplantation (n = 3, 6%) for advanced local disease. Forty-five (87%) received primary or neoadjuvant and/or adjuvant chemotherapy. Patients had the following CCG/POG stages: I (n = 31, 60%), II (n = 6, 11.5%), III (n = 9, 17%), and IV (n = 6, 11.5%). Complete gross resection (stage I and II) was achieved in 37 (71%) patients. The perioperative mortality and morbidity rates were 0% and 29%, respectively. Patients with complete resection had significantly better 5-year DSS and median survival compared with incomplete gross resection: 62% vs 9% and 216 vs 18 months, P < .001. Patients treated during the period 1995-2005 had better 5-year DSS and median survival compared with those treated during 1975-1994: 68% vs 32% and 117 vs 27 months, P = .032. All 3 patients who underwent transplantation for conventionally unresectable disease are alive without disease recurrence (follow-up period, 1-15 years).

CONCLUSION

Complete resection of the pediatric primary liver tumors remains the cornerstone of treatment to achieve cure. Major liver resection can be performed with minimal perioperative mortality and morbidity. Patients with HB appeared to have better survival compared with patients with HCC, and there was significant improvement in the DSS of children treated in the recent decade. Liver transplantation in conjunction with chemotherapy may have an increasing role in the management of locally advanced primary liver cancers.

Immunosuppressive agents in solid organ transplantation: Mechanisms of action and therapeutic efficacy

Effective immunosuppression is an essential pre-requisite for successful organ transplantation and improvements in outcome after transplantation have to a large extent been dependent on developments in immunosuppressive therapy. Here we provide an overview of the different immunosuppressive agents currently used in solid organ transplantation. A historical perspective on the development of immunosuppression for organ transplantation is followed by a review of the individual agents, with a focus on their mechanism of action and efficacy. Steroids, anti-proliferative agents (azathioprine and mycophenolate), calcineurin inhibitors (cyclosporine and tacrolimus) and TOR inhibitors (sirolimus and everolimus) are discussed along with both polyclonal and monoclonal antibody preparations. Many of the key clinical trials that underpin current clinical usage of these agents are described and side-effects of the different agents are highlighted. Finally, a number of newer agents still in various stages of clinical development are briefly considered.

Post-transplant lymphoproliferative disorders (PTLD) after solid organ transplantation

Post-transplant lymphoproliferative disorders (PTLD) are a well-recognised and potentially fatal complication after solid organ transplantation. They include a spectrum of disorders ranging from benign hyperplasia to invasive malignant lymphoma. The majority of cases are associated with Epstein Barr virus (EBV)-driven tumour formation in B cells and are a consequence of the detrimental effect of immunosuppressive agents on the immune-control of EBV. This review provides an update on the pathogenesis and clinical features of PTLD after solid organ transplantation and discusses recent progress in management. Reduction in immunosuppressive therapy remains a key component of therapy for EBV-positive PTLD and may lead to remission in early disease. Chemotherapy is used when reduced immunosuppression fails to control early disease and as initial therapy for many cases of late disease. Unfortunately, the mortality for PTLD that fails to respond to a reduction in immunosuppression remains high. Newer treatments include manipulation of the cytokine environment, B lymphocyte depleting antibodies and adoptive T cell immunotherapy using allogeneic or autologous EBV-specific cytotoxic T lymphocytes. Although early results appear promising, well-designed clinical trials are needed to assess the efficacy of these novel approaches. EBV vaccination may in the future prove an effective prophylaxis against EBV-driven PTLD but until then, avoiding excessive immunosuppressive therapy may help minimise the risk of PTLD.

Posttransplant survival in pediatric fulminant hepatic failure: the SPLIT experience

Pediatric patients with fulminant hepatic failure (FHF) tend to be the sickest and have the most urgent need for a liver transplant. The purpose of this analysis was to identify factors associated with posttransplant survival in this subset of patients. Data on all FHF patients registered in the Studies of Pediatric Liver Transplantation (SPLIT) registry from 1995 to 2002 were analyzed. Demographics such as age, gender, race, weight, and etiology of liver disease were recorded. Pretransplant degree of encephalopathy; intubation; dialysis; laboratory parameters such as serum bilirubin and international normalized ratio of coagulopathy (INR); and type of graft: cadaveric whole, cadaveric technical variant, or living donor were analyzed to determine effects on patient survival. Overall, FHF accounted for 12.9% (141 / 1,092) of primary transplants performed between 1995 and 2002. The etiology of liver disease was unknown in the vast majority of children (126 / 141; 89.4%). Mortality while on the waiting list for FHF children is significantly higher than for children with other liver disease (P < .0001). Six-month survival posttransplant for patients with FHF (74.5%) is significantly lower (P < .0001) than those with chronic liver disease (88.9%). A multivariate model demonstrates that the highest risk group includes those children with grade 4 encephalopathy (P < .0001), infants less than 1 year of age (P = .018), and children requiring dialysis prior to transplantation (P = .002). Pretransplant bilirubin and INR were not significant predictors of posttransplant survival after controlling for the other significant factors. Living donor and split / reduced grafts did not have a significantly increased risk of posttransplant death compared to whole grafts. In conclusion, despite advances in the surgical techniques and changes in organ allocation, pediatric patients with FHF continue to have a high pretransplant mortality and less successful posttransplant survival compared to children with chronic liver disease.

Clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplantation

The aim of this review is to analyse critically the recent literature on the clinical pharmacokinetics and pharmacodynamics of tacrolimus in solid organ transplant recipients. Dosage and target concentration recommendations for tacrolimus vary from centre to centre, and large pharmacokinetic variability makes it difficult to predict what concentration will be achieved with a particular dose or dosage change. Therapeutic ranges have not been based on statistical approaches. The majority of pharmacokinetic studies have involved intense blood sampling in small homogeneous groups in the immediate post-transplant period. Most have used nonspecific immunoassays and provide little information on pharmacokinetic variability. Demographic investigations seeking correlations between pharmacokinetic parameters and patient factors have generally looked at one covariate at a time and have involved small patient numbers. Factors reported to influence the pharmacokinetics of tacrolimus include the patient group studied, hepatic dysfunction, hepatitis C status, time after transplantation, patient age, donor liver characteristics, recipient race, haematocrit and albumin concentrations, diurnal rhythm, food administration, corticosteroid dosage, diarrhoea and cytochrome P450 (CYP) isoenzyme and P-glycoprotein expression. Population analyses are adding to our understanding of the pharmacokinetics of tacrolimus, but such investigations are still in their infancy. A significant proportion of model variability remains unexplained. Population modelling and Bayesian forecasting may be improved if CYP isoenzymes and/or P-glycoprotein expression could be considered as covariates. Reports have been conflicting as to whether low tacrolimus trough concentrations are related to rejection. Several studies have demonstrated a correlation between high trough concentrations and toxicity, particularly nephrotoxicity. The best predictor of pharmacological effect may be drug concentrations in the transplanted organ itself. Researchers have started to question current reliance on trough measurement during therapeutic drug monitoring, with instances of toxicity and rejection occurring when trough concentrations are within 'acceptable' ranges. The correlation between blood concentration and drug exposure can be improved by use of non-trough timepoints. However, controversy exists as to whether this will provide any great benefit, given the added complexity in monitoring. Investigators are now attempting to quantify the pharmacological effects of tacrolimus on immune cells through assays that measure in vivo calcineurin inhibition and markers of immunosuppression such as cytokine concentration. To date, no studies have correlated pharmacodynamic marker assay results with immunosuppressive efficacy, as determined by allograft outcome, or investigated the relationship between calcineurin inhibition and drug adverse effects. Little is known about the magnitude of the pharmacodynamic variability of tacrolimus.

Tacrolimus and steroids versus ciclosporin microemulsion, steroids, and azathioprine in children undergoing liver transplantation: randomised European multicentre trial

BACKGROUND

Results of studies in adult recipients of liver allograft suggest that tacrolimus is more efficacious than ciclosporin microemulsion in the prevention of acute rejection. We aimed to compare these drugs in children undergoing liver transplantation.

METHODS

This 12-month multicentre, open-label, parallel-group, randomised study compared a dual tacrolimus regimen (tacrolimus/corticosteroids, n=93) with a triple ciclosporin microemulsion regimen (ciclosporin microemulsion/corticosteroids/azathioprine, n=92) in children who had had liver transplants (age < or =16 years, bodyweight < or =40 kg). Initial oral daily doses were 0.30 mg/kg for tacrolimus and 10 mg/kg for ciclosporin microemulsion. Primary endpoint was the incidence of and time to first histologically proven acute rejection. We excluded patients from analysis if they did not receive the study drug, or were given incorrect medication. Otherwise patients were analysed in accordance with their random treatment allocation, irrespective of whether they switched medication during the trial.

FINDINGS

Median age was 22 months (IQR 9-56) in the tacrolimus group and 17 months (9-54) in the ciclosporin microemulsion group. We noted no difference between treatment groups with respect to patient survival (93.4% vs 92.2%; p=0.77) or graft survival (92.3% vs 85.4%; p=0.16) at month 12 after transplant. The acute rejection free rate at study end (Kaplan-Meier method) was 55.5% for patients on tacrolimus and 40.2% for patients on ciclosporin microemulsion (p=0.0288). The Kaplan-Meier estimate of patients free from corticosteroid-resistant acute rejection at study end was 94.0% for tacrolimus-treated patients and 70.4% for ciclosporin-microemulsion-treated patients (p<0.0001). Overall, incidence of adverse events did not differ between groups.

INTERPRETATION

Tacrolimus is a safe and effective treatment for the prevention of rejection after liver transplantation in children.

Sirolimus for pediatric liver transplant recipients with post-transplant lymphoproliferative disease and hepatoblastoma

Sirolimus is a promising immune suppressive agent, with the potential to reduce calcineurin inhibitor associated nephrotoxicity, halt progression of chronic rejection and prevent tumor proliferation. The aim of this study was to review the experience using sirolimus in pediatric liver transplant recipients at a single center. Database and medical charts of all pediatric liver transplant recipients receiving sirolimus at the Hospital for Sick Children in Toronto were reviewed. Eight patients received sirolimus between October, 2000 and September, 2002. Indications for using sirolimus were post-transplant lymphoproliferative disease (PTLD) (n = 6) and hepatoblastoma (n = 2). Two patients with PTLD concurrently had renal impairment and chronic rejection. Sirolimus dosages ranged between 1.5 and 5 mg once daily. Median duration of follow-up was 17 months. Persistently elevated liver transaminase levels in the two children with chronic rejection decreased during sirolimus therapy. Recurrence of PTLD occurred in one patient. Two patients were diagnosed with acute cellular rejection after transition to maintenance sirolimus monotherapy. Resolution of adverse effects including mouth sores (n = 3), leg swelling (n = 2) and hyperlipidemia (n = 3) occurred either spontaneously or with dose reduction. Sirolimus was discontinued in four patients because of persisting bone marrow suppression, interstitial pneumonitis, life-threatening sepsis and refractory diarrhea. Children with PTLD or hepatoblastoma may benefit from immune suppression with sirolimus after liver transplantation. Further multi-center, prospective, randomized controlled trials will be instrumental to further the knowledge of long-term efficacy, safety and tolerability of sirolimus for selected children following liver transplantation.

Current status of liver transplantation in children

There are two critical issues on opposite ends of the timeline for patients who are eligible for liver transplantation. On the one hand, the crisis in the cadaveric organ supply makes surviving to transplant ever more risky. On the other hand, patients who receive successful transplants face the consequences of long-term immunosuppression and its potentially life-threatening complications. The donor shortage is forcing difficult decisions that affect all patients who await liver transplantation. It is important to scrutinize carefully the results of all policies that govern allocation and the ethics of the solutions we advocate to ensure that no patient subgroup is being at a disadvantage. Current immunosuppression practices are being challenged by an increasing understanding of the immunologic events triggered by the allograft and the goal to free patients from consequences of a lifetime of immunosuppression. Clinicians can expect, and perhaps require, that new immunosuppressive protocols will address how the planned intervention might be expected to advance the understanding of tolerance mechanisms. As knowledge increases, clinicians can anticipate innovative new immunosuppressive proposals. Calcineurin and steroid-free induction, the use of donor-derived bone marrow infusion, recipient pretreatment, costimulatory blockade, and new antibody induction approaches are all being proposed--often in combination--for clinical trials. Researchers face additional challenges in defining endpoints if the goal is not just the short-term reduction in rejection but the minimization, and eventual discontinuation, of immunosuppressive drugs while maintaining excellent long-term graft function. How much "failure" will be accepted and how will it be defined? How will clinicians interpret liver biopsies if they begin to accept that some lymphocytic infiltrates may be beneficial mediators of the ongoing immune activation necessary for the maintenance of tolerance? How will they adjust immunosuppression practices to the dynamic processes in the immune response that maintain tolerance? Remarkable short-term successes in providing transplants for thousands of children with liver failure have brought these challenges into sharp focus. Clinicians must seek to move the life-giving science of transplantation toward a new goal: providing long lifetimes of excellent graft function with minimal toxicity from immunosuppressive drugs and the hope of freedom from immunosuppression altogether. Pediatric liver recipients, whose grafts have inherent tolerogenic potential and for whom we can anticipate decades of life after transplant, may prove to be an ideal study population to further these goals.

Hematologic abnormalities in liver-transplanted children during medium- to long-term follow-up

OBJECTIVE

Hematologic abnormalities as adverse effects related to immunosuppressive drugs in liver-transplanted children are rarely reported. We have observed anemia, neutropenia, and thrombocytopenia in our pediatric liver-transplant population. The aim of this study was to exclude all suspected etiologies to define the association of immunosuppressants with these abnormalities.

METHODS

Patients under 18 years old who still attend periodic controls at liver-transplant outpatient clinics were considered. Seventy patients met the inclusion criteria, 36 girls and 34 boys. Mean patient age was 5.6 years (range: 7 months to 17 years) and mean follow-up 6 years (range: 1-10 years). Medical records were reviewed beginning 1 month posttransplant. Treatment exposures, irradiation, blood product administration, and all laboratory studies were reviewed. When a hematologic abnormality was detected, we recorded the management for its resolution, the clinical response to therapy and the length of treatment.

RESULTS

Twenty-five of the 70 children suffered 26 abnormal hematologic episodes (anemia 14, neutropenia 2, thrombocytopenia 3, simultaneous anemia and neutropenia 5, and pancytopenia 2). Eleven episodes (42%) had unclear etiologies and the process of elimination suggested an association with the immunosuppressant. Switching immunosuppressant was required in four patients and dose reduction in seven.

CONCLUSIONS

Hematologic abnormalities in liver-transplanted children are common. The etiology is readily attributable to several causes. When the immunosuppressant appears to be a possible cause, the first step is dose reduction. If the hematologic abnormality persists despite dose reduction, a trial switch may be required.

The absence of chronic rejection in pediatric primary liver transplant patients who are maintained on tacrolimus-based immunosuppression: a long-term analysis

BACKGROUND

Although the outcome of liver transplantation has improved significantly during the past two decades, graft loss caused by chronic rejection after liver transplantation still occurs in 2% to 20% of recipients. The overall incidence of chronic rejection is also reported to be low in adult recipients, and risk factors have been identified. Chronic rejection is associated with the inability to maintain baseline immunosuppression. Additionally, the diagnoses of primary biliary cirrhosis, primary sclerosing cholangitis, autoimmune hepatitis, hepatitis B virus, and hepatitis C virus, common indications for liver transplantation in adults, are associated with a higher incidence of chronic rejection. Fortunately, these diagnoses are rarely seen in children. Little is known about chronic rejection in long-term pediatric liver transplant survivors. The purpose of this longitudinal study was to examine the incidence of biopsy-proven chronic rejection in long-term survivors of primary pediatric liver transplantation under tacrolimus-based immunosuppression.

METHODS

From October 1989 to December 1992, 166 children (boys=95, girls=71; mean age=5.0+/-2.9 years) received a primary liver transplant. These patients were followed until March 2000 with a mean follow-up of 9+/-0.8 (range, 7.4-10.4) years. All liver biopsy specimens and explanted grafts were evaluated for evidence of chronic rejection using the International Banff Criteria.

RESULTS

The mortality rate during the follow-up period was 15% (n=25). Retransplantation was required in 11% (n=18) of recipients. Actuarial patient and graft survival rates at 10 years were 84.9% and 80.1%, respectively. There were 535 liver biopsy samples available for evaluation, including the 18 explanted allografts. Biopsy specimens of three other functioning allografts showed evidence of chronic rejection. Immunosuppression had been discontinued or drastically reduced in these recipients because of life-threatening infections, noncompliance, or both. On restoring baseline immunosuppression, all three children had normalized liver function and the allografts were maintained; the liver transplant patients who are alive currently have normal liver functions.

CONCLUSION

The findings of this study suggest that chronic rejection does not occur in pediatric liver transplant recipients receiving tacrolimus-based immunosuppression, provided baseline immunosuppression is maintained.

Bayesian forecasting and prediction of tacrolimus concentrations in pediatric liver and adult renal transplant recipients

AIM

To test the predictive capacity of two recently derived population pharmacokinetic models and the usefulness of Bayesian forecasting to predict tacrolimus blood concentrations in pediatric liver and adult kidney transplant recipients.

MATERIALS AND METHODS

New databases were added to the Abbottbase PKS (Bayesian dosage prediction) program to incorporate the population pharmacokinetic models developed for tacrolimus. Two independent populations of transplant recipients were used to predict tacrolimus trough concentrations. Pharmacokinetic, demographic, and covariate data were collected from patient records. Different time weighting factors were tested (1, 1.005, 1.01) and the influence of excluding data collected in the first 5 days post-transplant examined. Concentrations were predicted until the 10th tacrolimus measurement. Actual tacrolimus concentrations were compared with those predicted by the PKS program and bias and precision determined.

RESULTS

Tacrolimus concentrations predicted by the PKS program were, on average, unbiased for the pediatric liver population, but were over-predicted (9%) for the adult renal population. In both populations predictions were not precise (imprecision ranged from 39 to 50%).

CONCLUSIONS

Due to the imprecision seen in this study, these models could not be used in clinical practice in the immediate post-transplant period. Poor precision may be due to reliance on routine drug monitoring data alone, difficulties with expression of covariates in continuous modeling relationships in the PKS program, lack of accurate quantitative measures of liver function, or large, random intraindividual variability in the bioavailability of tacrolimus.

Long-term comparison of tacrolimus- and cyclosporine-induced nephrotoxicity in pediatric heart-transplant recipients

Nephrotoxicity is an adverse effect of cyclosporine and tacrolimus. Studies comparing their long-term nephrotoxicities are lacking. This study evaluates the nephrotoxicity of these agents over a 7-year period following heart transplantation. Pediatric heart-transplant recipients receiving cyclosporine or tacrolimus as primary immunosuppression were evaluated at two centers from 1982 to 1998. Data collected included serum creatinine, height and weight prior to transplantation, at 1 and 6 months and 1 years post transplantation, and at yearly intervals thereafter. Creatinine clearance was calculated and compared between the two groups. Glomerular filtration rate was measured using Tc-99m diethylenetriaminepentacetic acid. In total, 123 patients were evaluated. Demographic data of the two groups were comparable. Creatinine clearance demonstrated a steady decline. This decline did not differ statistically between the two groups: tacrolimus 98.9 and 90.7mL/min/1.73 m2 at 1 month and 5 years, respectively; cyclosporine 110.7 and 81.7 mL/min/ 1.73 m2 at 1 month and 5 years, respectively. Four patients developed end-stage renal failure. Calculated creatinine clearance consistently overestimated glomerular filtration rate, the latter being greater than 2 standard deviations below the mean normal in 38% of patients. We conclude that the nephrotoxicities of tacrolimus and cyclosporine are comparable over the medium- to long-term in pediatric heart-transplant recipients.

Conversion from cyclosporin to tacrolimus in paediatric liver transplant recipients

Substitution of cyclosporin with tacrolimus should be considered for paediatric liver transplant recipients with cyclosporin-associated complications such as hypertension, gum hyperplasia, hirsutism, gynaecomastia and growth retardation, as well as recurrent or refractory acute rejection, chronic duct injury or chronic rejection. Continued experience with well tolerated drug administration and careful monitoring during drug substitution has limited drug toxicity associated with tacrolimus to a level comparable to or less than that associated with cyclosporin. Successful outcome with long term graft salvage has been reported in up to 80% of patients converted to tacrolimus because of acute rejection and 50% of patients converted because of chronic rejection. Nearly all children converted because of cyclosporin-related complications have a successful outcome. Additional benefits of conversion to tacrolimus include improvement in growth and resolution of hypertension, hirsutism and cushingoid facies. Complete corticosteroid withdrawal is possible in up to 78% of children post-conversion. Long term outcome in these patients may be optimised by conversion to tacrolimus at an early stage of acute or chronic transplant rejection in order to minimise the cumulative amount of immunosuppression. Avoidance of cyclosporin-related toxicity and minimisation of corticosteroid therapy may further improve patient compliance to drug therapy.

Management of the pediatric liver transplant patient

1. In pretransplant management, the prevention and treatment of malnutrition is essential for pediatric patients as malnutrition is associated with both increased pre- and posttransplant mortality. 2. Technical complications, particularly hepatic artery thrombosis, after pediatric liver transplantation are relatively common given the small size of the majority of the recipients. Early recognition is essential to reduce the associated increased risk for both patient and graft loss. 3. Immunosuppression regimens in children should aim to begin weaning of steroids within the first year after transplant because of their detrimental impact on growth. 4. Long-term immunosuppression strategies must focus on avoiding the risks of long-term immunosuppression, particularly nephrotoxicity, neurotoxicity, de novo malignancy, and late infections. 5. EBV-associated PTLD is a special problem for young pediatric liver recipients. Strategies for prevention and preemptive management are essential. 6. Noncompliance in teens is a particular problem and is associated not only with graft dysfunction, but also with graft loss and patient death. Recognizing teens at risk and providing intervention strategies require a multi-disciplinary approach.

Risk factors for chronic rejection after pediatric liver transplantation

BACKGROUND

Chronic rejection is a major cause of graft failure and a frequent reason for retransplantation after pediatric liver transplantation. Identification of risk factors for chronic rejection in pediatric transplant recipients is vital to understanding the pathogenesis of chronic rejection and may help prevent further graft loss.

METHODS

The study population consisted of 285 children with 385 liver transplants performed at University of Chicago between 1991 and 1999. Logistic regression analysis was used to evaluate risk factors for chronic rejection, including age, sex, race, type of graft (living related vs. cadaveric), native liver disease, acute rejection episodes, cytomegalovirus (CMV) infection, and posttransplant lymphoproliferative disease (PTLD).

RESULTS

The chronic rejection rate was significantly lower in recipients of living-related grafts than in recipients of cadaveric grafts (4% vs. 16%, P=0.001). African-American recipients had a significantly higher rate of chronic rejection than did Caucasian recipients (26% vs. 8%, P<0.001). Numbers of acute rejection episodes, transplantation for autoimmune disease, occurrence of PTLD, and CMV infection were also significant risk factors for chronic rejection. However, recipient age, gender, donor-recipient gender mismatch, and donor-recipient ethnicity mismatch were not associated with higher incidence of chronic rejection

CONCLUSION

We have identified a number of risk factors for chronic rejection in a large group of pediatric liver allograft recipients. We believe that donor-recipient matching for gender or race is not likely to reduce the incidence of chronic rejection. The elucidation of the mechanisms by which living-related liver transplantation affords protection against chronic rejection may provide insight into the immunogenetics of chronic rejection and help prevent further graft loss.

Population pharmacokinetics of tacrolimus in children who receive cut-down or full liver transplants

BACKGROUND

The aim of this study was to investigate the population pharmacokinetics of tacrolimus in pediatric liver transplant recipients and to identify factors that may explain pharmacokinetic variability.

METHODS

Data were collected retrospectively from 35 children who received oral immunosuppressant therapy with tacrolimus. Maximum likelihood estimates were sought for the typical values of apparent clearance (CL/F) and apparent volume of distribution (V/F) with the program NONMEM. Factors screened for influence on the pharmacokinetic parameters were weight, age, gender, postoperative day, days since commencing tacrolimus therapy, transplant type (whole child liver or cut-down adult liver), liver function tests (bilirubin, alkaline phosphatase [ALP], aspartate aminotransferase [AST], gamma-glutamyl transferase [GGT], alanine aminotransferase [ALT]), creatinine clearance, hematocrit, corticosteroid dose, and concurrent therapy with metabolic inducers and inhibitors of tacrolimus.

RESULTS

No clear correlation existed between tacrolimus dosage and blood concentrations (r2=0.003). Transplant type, age, and liver function test values were the most important factors (P<0.01) that influenced the pharmacokinetics of tacrolimus. CL/F estimates were greater in whole liver recipients, decreased with increasing patient age and AST values, and increased with increasing GGT values. Average parameter estimates were CL/F=5.75 L/h (cut-down liver), CL/F=44 L/h (whole liver), and V/F=617 L. Marked intersubject variability (CV%=110% to 297%) and residual variability (CV%=42%) was observed.

CONCLUSIONS

Pharmacokinetic information obtained in this study may assist physicians in making individualized dosage decisions in regard to tacrolimus in pediatric liver transplant recipients. Children who received a whole child's liver appeared to retain "pediatric" clearance, whereas those who received a cut-down adult liver had "adult" clearances (on average 7-fold less).

CD4+ T-cell effectors inhibit Epstein-Barr virus-induced B-cell proliferation

In immunodeficient hosts, Epstein-Barr virus (EBV) often induces extensive B-cell lymphoproliferative disease and lymphoma. Without effective in vitro immune surveillance, B cells infected by the virus readily form immortalized cell lines. In the regression assay, memory T cells inhibit the formation of foci of EBV-transformed B cells that follows recent in vitro infection by EBV. No one has yet addressed which T cell regulates the early proliferative phase of B cells newly infected by EBV. Using new quantitative methods, we analyzed T-cell surveillance of EBV-mediated B-cell proliferation. We found that CD4+ T cells play a significant role in limiting proliferation of newly infected, activated CD23+ B cells. In the absence of T cells, EBV-infected CD23+ B cells divided rapidly during the first 3 weeks after infection. Removal of CD4+ but not CD8+ T cells also abrogated immune control. Purified CD4+ T cells eliminated outgrowth when added to EBV-infected B cells. Thus, unlike the killing of EBV-infected lymphoblastoid cell lines, in which CD8+ cytolytic T cells play an essential role, prevention of early-phase EBV-induced B-cell proliferation requires CD4+ effector T cells.

Liver transplantation. The pediatric challenge

Successful liver transplantation in a child is often a hard-won victory, requiring all the combined expertise of a dedicated pediatric transplant team. This article outlines the considerable challenges still facing pediatric liver transplant physicians and surgeons. In looking to the future, where should priorities lie to enhance the success already achieved? First, solutions to the donor shortage must be sought aggressively by increasing the use of from split-liver transplants, judicious application of living-donor programs, and increasing the donation rate, perhaps by innovative means. The major immunologic barriers, to successful xenotransplantation make it unlikely that this option will be tenable in the near future. Second, current immunosuppression is nonspecific, toxic, and unable to be individually adjusted to the patient's immune response. The goal of achieving donor-specific tolerance will require new consideration of induction protocols. Developing a clinically applicable method to measure the recipient's immunoreactivity is of paramount importance, for future studies of new immunosuppressive strategies and to address the immediate concern of long-term over-immunosuppression. The inclusion of pediatric patients in new protocols will require the ongoing insistence of pediatric transplant investigators. Third, the current immunosuppressive drugs have a long-term morbidity and mortality of their own. These long-term effects are particularly important in children who may well have decades of exposure to these therapies. There is now some understanding of their long-term renal toxicity and the risk of malignancy. New drugs may obviate renal toxicity, whereas the risk of malignancy is inherent in any nonspecific immunosuppressive regimen. Although progress is being made in preventing and recognizing PTLD, this entity remains an important ongoing concern. The global effect of long-term immunosuppression on the child's growth, development, and intellectual potential is unknown. Of particular concern is the potential for neurotoxicity from the calcineurin inhibitors. Fourth, recurrent disease and new diseases, perhaps potentiated by immunosuppressive drugs, must be considered. Already the recurrence of autoimmune disease and cryptogenic cirrhosis have been documented in pediatric patients. Now, a new lesion, a nonspecific hepatitis, sometimes with positive autoimmune markers, that may progress to cirrhosis has been recognized. It is not known whether this entity is an unusual form of rejection, an unrecognized viral infection, or a response to immunosuppressive drugs themselves. Finally, pediatric transplant recipients, like any other children, must be protected and nourished physically and mentally if they are to fulfill their potential. After liver transplantation the child's growth, intellectual functioning, and psychologic adaptation may all require special attention from parents, teachers, and physicians alike. There is limited understanding of how the enormous physical intervention of a liver transplantation affects a child's cognitive and psychologic function as the child progresses through life. The persons caring for these children have the difficult responsibility of providing services to evaluate these essential measures of children's health over the long term and to intervene if necessary. Part of the transplant physician's our duty to protect and advocate for children is to fight for equal access to health care. In most of the developing world, economic pressures make it impossible to consider liver transplantation a health care priority. In the United States and in other countries with the medical infrastructure to support liver transplantation, however, health care professionals must strive to be sure that the policies governing candidacy for transplantation and allocation of organs are applied justly and uniformly to all children whose lives are threatened by liver disease. In the current regulatory climate that increasingly takes medical decisions out of the hands of physicians, pediatricians must be even more prepared to protect the unique and often complicated needs of children both before and after transplantation. Only in this way can the challenges of the present and the future be met.

Comparative long-term evaluation of tacrolimus and cyclosporine in pediatric liver transplantation

BACKGROUND

In this report, we compare the long-term outcome of pediatric liver transplantation (LTx) patients maintained with tacrolimus-based and with cyclosporine (CsA)-based immunosuppressive therapy. We examine long-term patient and graft survival, the incidence of rejection, and immunosuppression-related complications.

METHOD

There were 233 consecutive primary LTx in children (ages <18 years) performed between October 1989 and December 1994 with tacrolimus-based immunosuppressive therapy (Group I). These were compared with 120 consecutive primary LTx performed with CsA-based immunosuppressive therapy between January 1988 and October 1989(Group II). Children in both groups were followed until July 1999. Mean follow-up was 91.41+/-17.7 months (range 55.6-117.8) for Group I, and 128+/-6.1 months (range 116.7-138.6) for Group II.

RESULTS

At 9 years of follow-up, actuarial patient and graft survival were significantly improved (patient survival 85.41% in Group I vs. 63.8% in Group II, P=0.0001; graft survival Group I 78.9% vs. 60.8% Group II, P=0.0003) and the rate of re -transplantation was significantly lower among patients in Group I (12% in Group I vs. 22.5% in Group II P=0.01). Children in Group I also experienced a significantly reduced incidence of acute rejection (0.97 per patient Group I vs. 1.5 per patient Group II P=0.002) and significantly less steroid resistant acute rejection episodes (3.1% in Group I vs. 8.6% in Group II P=0.0001). The mean steroid dose was significantly lower in Group I compared with Group II at all time points (P=0.0001) after LTx. Freedom from steroid was also significantly higher in Group I compared with Group II at all time points after LTx (ranging from 78% to 84% in Group I and 9% to 32% in Group II during a 1- to 7-year posttransplant period P=0.0001). The rate of hypertension was significantly lower in Group I than Group II (P=0.0001), and the severity of hypertension (need for more than one anti-hypertensive medication) was also significantly lower in Group I than Group II (P=0.0001). Although the rate of posttransplant lymphoproliferative disorder (PTLD) was not significantly different (13.7% Group I vs.8.3% Group II, P=0.13), the survival after PTLD was significantly better for Group I at 81.2% than for Group II at 50% after 5 years (P=0.034). Conclusion. The results suggest that tacrolimus-based therapy provides significant long-term benefit to pediatric LTx patients, evidenced by significantly improved patient and graft survival, reduced rate of rejection, and hypertension with lower steroid doses.

Long-term results after conversion from cyclosporine to tacrolimus in pediatric liver transplantation for acute and chronic rejection

Tacrolimus is beneficial in liver transplantation for reversing steroid-resistant acute rejection, and for controlling the process of chronic rejection in allograft recipients receiving Cyclosporine- (CyA) based regimens. Very little is known about the long-term efficacy of tacrolimus in pediatric transplantation after conversion from CyA. Our study examines the long-term outcome after conversion to tacrolimus for acute or chronic rejection in pediatric liver transplant (LTx) recipients.

METHOD

Seventy-three children (age < 18 years) receiving their primary LTx under CyA between August 1989 and April 1996 were converted to tacrolimus for ongoing acute rejection (n=22, group I) or chronic rejection (n=51, group II). Mean age at the time of conversion was 10.2+/-5.5 years with a mean interval from LTx to conversion of 3.5+/-2.9 (range 0.5-10.1 years). There were 33 boys and 40 girls. All patients were followed until June 1999. Mean follow-up was 97.3+/-17.4 months (range 62.4-118.9 months).

RESULTS

Overall 5-year actual patient survival was 78.1% and 8-year actuarial survival was 74.6%. Patients converted to tacrolimus therapy to resolve acute rejection (group I) experience significantly better patient and graft survival at 5 and 8 years than those converted to resolve chronic rejection (group II). Eight-year patient survival and graft survival was 95.5 and 90.9% for group I compared to 74.6 and 53.5% for group II, respectively (long rank P=0.035 and 0.01, respectively). Nearly 75% of children were weaned off steroids after conversion. There was a marked improvement in hypertension, gum hyperplasia, hirsutism, and cushingoid appearance. One child in group I (4.5%) and four children in group II (7.8%) developed posttransplant lymphoproliferative disorder after conversion. There was an improvement in growth in children who were less than the age of 12 years at the time of conversion and who were weaned off steroids; more significantly girls responded more favorably than boys.

CONCLUSION

The benefit of transplantation is maintained long-term after conversion to tacrolimus for acute or chronic rejection. The response rate was significantly better in group I as compared with group 11. Marked improvement in growth, hypertension, and reversal of the brutalizing effects of CyA was noted after conversion to tacrolimus. The results suggest that early conversion of pediatric liver transplant patients is warranted for the treatment of acute and chronic rejection, and for improvements in quality of life.