The potential role of rapamycin in pediatric transplantation as observed from adult studies

The safety of available treatments options for neuroendocrine tumors

INTRODUCTION

Neuroendocrine neoplasms (NEN) represent a heterogeneous group of malignancies generally characterized by low proliferation and indolent course. However, about half of the newly diagnosed cases are metastatic and require long-term systemic therapies. Areas covered: This review revises the literature to summarize the current knowledge upon safety of all systemic treatment options available. Thirty three different clinical studies have been considered, including 4 on somatostatin analogues (SSA), 5 on targeted therapies, 10 on peptide receptor radionuclide therapy (PRRT), and 14 on chemotherapy. Expert opinion: SSA are safe and well tolerated without any relevant severe adverse event and very low treatment discontinuation rate. Targeted therapies show a satisfying safety profile. Most adverse events are grade 1-2 and easy manageable with dose reduction or temporary interruption. PRRT is manageable and safe with a low rate of grade 3-4 adverse events. However, severe renal and hematologic toxicity may occur. Chemotherapy is usually considered after previous therapeutic lines. Therefore, these subjects are more susceptible to experience adverse events due to cumulative toxicities or poor performance status. The available systemic treatment options are generally well tolerated and suitable for long-term administration. Cumulative toxicity should be taken in account for the definition of therapeutic sequence.

Pooled population pharmacokinetic model of imipenem in plasma and the lung epithelial lining fluid

AIMS

Several clinical trials have confirmed the therapeutic benefit of imipenem for treatment of lung infections. There is however no knowledge of the penetration of imipenem into the lung epithelial lining fluid (ELF), the site of action relevant for lung infections. Furthermore, although the plasma pharmacokinetics (PK) of imipenem has been widely studied, most studies have been based on selected patient groups. The aim of this analysis was to characterize imipenem plasma PK across populations and to quantify imipenem ELF penetration.

METHODS

A population model for imipenem plasma PK was developed using data obtained from healthy volunteers, elderly subjects and subjects with renal impairment, in order to identify predictors for inter-individual variability (IIV) of imipenem PK. Subsequently, a clinical study which measured plasma and ELF concentrations of imipenem was included in order to quantify lung penetration.

RESULTS

A two compartmental model best described the plasma PK of imipenem. Creatinine clearance and body weight were included as subject characteristics predictive for IIV on clearance. Typical estimates for clearance, central and peripheral volume, and inter-compartmental clearance were 11.5 l h(-1) , 9.37 l, 6.41 l, 13.7 l h(-1) , respectively (relative standard error (RSE) <8%). The distribution of imipenem into ELF was described using a time-independent penetration coefficient of 0.44 (RSE 14%).

CONCLUSION

The identified lung penetration coefficient confirms the clinical relevance of imipenem for treatment of lung infections, while the population PK model provided insights into predictors of IIV for imipenem PK and may be of relevance to support dose optimization in various subject groups.

Role of mTOR1 and mTOR2 complexes in MEG-01 cell physiology

The function of the mammalian target of rapamycin (mTOR) is upregulated in response to cell stimulation with growing and differentiating factors. Active mTOR controls cell proliferation, differentiation and death. Since mTOR associates with different proteins to form two functional macromolecular complexes, we aimed to investigate the role of the mTOR1 and mTOR2 complexes in MEG-01 cell physiology in response to thrombopoietin (TPO). By using mTOR antagonists and overexpressing FKBP38, we have explored the role of both mTOR complexes in proliferation, apoptosis, maturation-like mechanisms, endoplasmic reticulum-stress and the intracellular location of both active mTOR complexes during MEG-01 cell stimulation with TPO. The results demonstrate that mTOR1 and mTOR2 complexes play different roles in the physiology of MEG-01 cells and in the maturation-like mechanisms; hence, these findings might help to understand the mechanism underlying generation of platelets.

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.

Early experience with conversion to sirolimus in a pediatric renal transplant population

Sirolimus is an immunosuppressive agent that offers potentially significant benefits for young transplant patients facing life-long treatment. Its action of reducing cell proliferation may reduce the risk of chronic allograft nephropathy and posttransplant neoplasia. Twenty-nine children were converted from calcineurin inhibitors to sirolimus after renal transplantation and followed for a minimum of 12 months. Glomerular filtration increased transiently in those converted before 12 months after transplantation but not in those converted later, when chronic histological changes had developed. Mild acute rejection occurred after conversion in 10%, and side effects led to cessation of sirolimus in 31%. Anemia occurred in 55% of patients and responded well to darbepoetin. Most side effects (anemia, hypercholesterolemia, mouth ulcers, and myalgias) became less severe with time. The number of antihypertensive drugs required decreased significantly on sirolimus. Although side effects are frequent on sirolimus, in the majority of children, they are mild enough to allow the patient to continue taking the drug, and for these children the long-term benefits are potentially valuable.

Conversion from calcineurin inhibitor to sirolimus in pediatric chronic allograft nephropathy

CAN is a major cause for allograft loss in renal transplantation. Sirolimus was recently introduced as a potent non-nephrotoxic alternative to CNIs. In the present study, effects of a conversion protocol were investigated in pediatric CAN with declining GFR, defined by a Schwartz formula clearance below 60 mL/1.73 m2/min, steadily increasing SCr and allograft biopsy. In eight children with a median age of 12.8 yr, sirolimus was started at median 32 months after transplantation with a loading dose of 0.24 mg/kgBW, followed by 0.2 mg/kgBW/day, aimed at trough levels of 15-20 ng/mL. CNIs were reduced to 50% at start of sirolimus and discontinued at median seven days when target levels of sirolimus were reached. Following conversion, changes of GFR significantly stabilized (-2.9 vs. +0.4 mL/min/1.73 m2/month, p = 0.025). Individual GFR increased in five of eight patients (p = 0.026), only one child exhibited unaltered progression of graft failure. In the responders, mean SCr improved by 0.3 mg/dL (p = 0.043). Effects were not dependent on GFR at conversion, nor time post-transplantation. Blood pressure, hematological parameters and proteinuria remained stable during the observation period, serum lipids transiently increased. About half of the children suffered from infectious complications. No child had to be taken off sirolimus; there was no graft loss during the observation period. In conclusion, conversion from CNIs to sirolimus is an effective protocol with tolerable side effects to stabilize renal graft function for at least one yr in the majority of children with biopsy proven CAN.

Conversion from calcineurin inhibitor to sirolimus in pediatric chronic allograft nephropathy

Chronic allograft nephropathy is a major cause for allograft loss in renal transplantation. Sirolimus was recently introduced as a potent non-nephrotoxic alternative to calcineurin inhibitors. In the present study, effects of a conversion protocol were investigated in pediatric chronic allograft nephropathy with declining glomerular filtration rate (GFR), defined by a Schwartz formula clearance below 60 mL/1.73 m(2)/min, steadily increasing serum creatinine and allograft biopsy. In eight children with a median age of 12.8 yr, sirolimus was started at median 32 months after transplantation with a loading dose of 0.24 mg/kg bodyweight (BW), followed by 0.2 mg/kgBW/day, aimed at trough levels of 15-20 ng/mL. Calcineurin inhibitors were reduced to 50% at the start of sirolimus and discontinued at median 7 days when target levels of sirolimus were reached. Following conversion, changes of GFR significantly stabilized (-2.9 vs. +0.4 mL/min/1.73 m(2)/month, p = 0.025). Individual GFR increased in five out of eight patients (p = 0.026), and only one child exhibited unaltered progression of graft failure. In the responders, mean serum creatinine improved by 0.3 mg/dL (p = 0.043). Effects were not dependent on GFR at conversion, or on time post-transplantation. Blood pressure, hematological parameters and proteinuria remained stable during the observation period, and serum lipids increased transiently. About half of the children suffered from infectious complications. No child had to be taken off sirolimus; there was no graft loss during the observation period. In conclusion, conversion from calcineurin inhibitors to sirolimus is an effective protocol with tolerable side effects to stabilize renal graft function for at least one yr in the majority of children with biopsy-proven chronic allograft nephropathy.

Sirolimus immunosuppression in pediatric heart transplant recipients: A single-center experience

BACKGROUND

Sirolimus has been used in heart transplant recipients for treatment of rejection, alternative immunosuppression (IS) and promotion of regression and prevention of graft vasculopathy (coronary artery disease [CAD]). This study reports on our center's experience with 16 children who underwent heart transplantation.

METHODS

Data were obtained by retrospective review.

RESULTS

Median age at time of review was 12.3 years (n = 16, 5.1 to 18.0 years; 9 boys, 7 girls), and at time of transplant 7.5 years (6 months to 18.0 years). Median time of sirolimus introduction was 2.7 years (1 month to 8.2 years) post-transplant. Fifteen patients were on steroids, 10 on tacrolimus (FK) and mycophenolate mofetil (MMF), 5 on FK and 1 on MMF with no calcineurin inhibitors (CNIs). The average dose of sirolimus was 0.25 mg/kg or 7.0 mg/m(2) to maintain a target level of 5 to 15 mug/liter. Sirolimus was started for CAD in 6 patients (38%), rejection in 5 (31%), and in 5 with combinations of CNI intolerance, CAD, renal dysfunction and rejection. All 6 who received sirolimus for rejection (International Society for Heart and Lung Transplantation [ISHLT] Grade 3A) showed improvement on follow-up biopsies. Two of 3 who received sirolimus for renal dysfunction showed improvement (glomerular filtration rate [GFR] 43 to 67 and 32 to 106 ml/min per 1.73 m(2), respectively). Side effects included hyperlipidemia (38%), abdominal pain (31%), mouth ulcers (26%), anemia or neutropenia (12.5%), persistent pericardial effusion (6%) and interstitial lung disease (6%). Sirolimus therapy was discontinued in 3 patients due to side effects.

CONCLUSIONS

In this study sirolimus was found to be a valuable IS agent for the management of rejection, significant renal dysfunction and CNI side effects. These results support the need for prospective studies of the role of sirolimus in primary rejection prophylaxis, primary CAD prophylaxis and CAD regression. There also exists a need to establish an adverse event profile for this drug.

Current immunosuppressive agents in pediatric renal transplantation: efficacy, side-effects and utilization

Advances in immunosuppressive therapy over the past decade have led to dramatic improvements in graft survival. The immunosuppression that is used is center-dependent and is constantly evolving with the development of new medications. The goal remains to find the best combination that will optimize graft survival, while minimizing the adverse effects.

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.

Cyclosporine in pediatric kidney transplantation

Before the era of cyclosporine (CsA), immunosuppression with azathioprine and steroids resulted in high rejection rates and severe growth retardation in pediatric renal transplant recipients. In the early 1980s, immunosuppression with CsA was introduced for children. Because of differences in metabolism rates and relation of weight and body surface area, special pediatric dosing regimens and monitoring strategies had to be developed. Use of CsA led to a decreased number of acute rejections and, consequently, to a marked increase in graft survival rates. The growth rates of transplanted children were significantly higher under CsA-based immunosuppression than with classical regimens. This was due to a decreased need of steroid co-administration. Main side effects of CsA in children were nephrotoxicity and hirsutism. The introduction of CsA microemulsion in the 1990s led to more reliable absorption profiles and to a lower interindividual variability of CsA area-under-the-curve concentrations and thus to another improvement in rejection rates. New monitoring strategies, based on CsA levels taken 2 hours' postdose, seem promising. In pediatric transplantation, CsA is often successfully combined with an antibody-induction therapy in order to reduce the number of early acute rejections. Combination with mycophenolate mofetil reduces the appearance of chronic rejection. Additional therapy with ToR inhibitors might enforce a reduction of CsA doses and therefore lead to a reduction of CsA toxic effects.

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.

Current immunosuppressive agents: efficacy, side effects, and utilization

Advances in immunosuppressive therapy over the past decade have led to dramatic improvements in graft survival. With the development of new agents, the focus of the transplant community is to establish regimens that maintain excellent graft survival rates but with fewer toxicities including infection, nephrotoxicity, malignancy, and cosmetic effects. Examples include the use of steroid-free protocols and calcineurin avoidance regimens, which are currently being studied by NAPRTCS. The ultimate goal of transplant immunosuppressive therapy is the induction of tolerance. As we learn more about immune function from basic and clinical research, tolerance to allografts seems a more reachable goal.

Therapy for acute rejection in pediatric organ transplant recipients

Despite the availability of potent immunosuppressive drugs, rejection after organ transplantation in children remains a serious concern, and may lead to significant morbidity, graft loss, and death of the patient. Acute graft rejection in pediatric recipients is first treated with methylprednisolone pulses, followed by progressive taper of corticosteroid doses. After control of the rejection episode, baseline immunosuppression has to be adjusted and closely monitored since rejection (especially late episodes, occurring more than 6 months after transplantation) may be due to a lack of compliance or sub-therapeutic drug concentrations. The management of corticosteroid resistant rejection is not standardized, and depends on the transplanted organ and previous immunosuppressive regimen. In patients experiencing corticosteroid resistant acute rejection while on a cyclosporine-based immunosuppressive regimen, cyclosporine is generally changed to tacrolimus. In case of tacrolimus-based immunosuppression, tacrolimus blood levels may be increased, and/or mycophenolate mofetil (which nowadays tends to replace azathioprine) or sirolimus may be added, although pharmacodynamic data and clinical studies with these agents are still scarce in pediatric recipients. The use of antithymocyte globulins or monoclonal anti-CD3 antibodies, muromonab CD3 (OKT3) is hampered by numerous adverse effects, including a significant risk of over-immunosuppression. These therapies are nowadays indicated in very selected cases. Other treatments such as plasmapheresis and high dose immunoglobulins may be useful in difficult cases. In patients with refractory rejection despite therapeutic escalation, the risks of over-immunosuppression, including opportunistic infections and malignancies (especially the Epstein-Barr virus related post-transplant lymphoproliferative disease) have to be balanced with the consequences of graft loss due to rejection. Detransplantation or retransplantation may, in some instances, be preferable to severe infectious or tumoral complications.

New approaches to hematopoietic cell transplantation for hematological diseases in children

Hematopoietic cell transplantation (HCT) has been used for more 30 years for the treatment of selected malignant and nonmalignant diseases. Traditionally, HCT for hematological disorders has relied on myeloablative conditioning before HLA-identical sibling bone marrow transplantation to correct the underlying hematological defect. Most children with hematological diseases who are referred to HCT have features that portend significant morbidity and early mortality. Among SAA patients who have HLA-identical sibling donors, younger patients with profound pancytopenia might be considered early for HCT. For others who lack sibling donors, patients who receive HCT from alternate sources have generally failed one or more courses of intensive immunosuppressive therapy and remain transfusion-dependent, some with hemosiderosis, red cell alloimmunization, and platelet transfusion refractoriness [44,46,48]. Currently, HCT for SCD is generally restricted to those who have experienced a significant sickle-related complication such as stroke, recurrent acute chest syndrome, or recurrent painful episodes [7,13]. In contrast, most reserve HCT in thalassemia for younger, Lucarelli class I, good-risk patients who have HLA-identical sibling donors, and veer away from older, high-risk thalassemics for whom transplantation is a riskier clinical intervention. For groups such as young adults with thalassemia major, HCT might become more widely applicable if its toxicity was reduced. Several approaches undergoing development include reduced-intensity conditioning and attempts to prevent GVHD. New methods to reduce the intensity and toxicity of conditioning as well as to use highly purified stem cells with the reduction in graft versus host disease may allow for the use of matched unrelated donors or haploidentical donors. This would serve to provide potentially more children who could benefit from stem cell transplantation with donors. These advances will hopefully lead to benefits for the majority of children who lack HLA-identical donors.

Single-dose pharmacokinetics and tolerability of everolimus in stable pediatric renal transplant patients

Everolimus (Certican; RAD), a novel macrolide with potent immunosuppressive and anti-proliferative activities, prevents acute rejection in adult recipients of renal transplantation. This phase I trial conducted in stable pediatric renal transplant patients examined the single-dose pharmacokinetics, safety, and tolerability of everolimus in combination with cyclosporin A (CsA; Neoral) and corticosteroids, with or without azathioprine. Nineteen pediatric patients were enrolled and received a single 1.2 mg/m2 dose of everolimus. Everolimus was safe and well tolerated, with a low incidence of adverse events reported and none judged to be related to the study medication. Everolimus administration did not increase infection rates or produce clinically significant changes in vital signs or changes in electrocardiograms. Apparent clearance and volume of distribution of everolimus increased with age, weight, and body surface area in a generally linear manner across the pediatric demographic ranges. Compared with adults from a previous study, apparent clearance (L/h) and distribution volume (L) were lower in pediatric patients, whereas the elimination half-life was similar. Single-dose everolimus co-administration did not affect the steady-state pharmacokinetics of CsA. Based on this information, pediatric patients will need a dose scaled down for body size, but can probably maintain the same twice-daily dosing schedule used in adults.

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.

Progress in renal transplantation for children

Renal transplantation continues to be the goal of therapy for children with end-stage renal disease. Patient age, primary renal disease, psychosocial status, living versus cadaver donor allograft, immunosuppressive therapy, urologic status, and maximization of growth and development must be considered in determining the optimal time for transplantation. Immunizations should be up to date, and the immune status of both the donor and the recipient with regard to Epstein Barr virus (EBV), cytomegalovirus (CMV), varicella, human immunodeficiency virus (HIV) and Hepatitis A, B, and C must be known. Prednisone; cyclosporine or tacrolimus; and mycophenolate mofetil or azathioprine remain the mainstays of immunosuppression. However, new therapies such as sirolimus are under investigation for use in pediatric renal transplantation. Induction therapies include T-cell antibodies as well as the more recent addition of interleukin-2 receptor blockers. Complications including infection, rejection, and malignancy continue to be problematic in pediatric renal transplantation. There continues to be a strong focus on optimizing growth and development after transplant. Although patient and graft survival have improved over time, outcomes in pediatric renal transplantation continue to lag behind those in adults.