Solid tumors following kidney transplantation in children.

Kidney transplant recipients have an increased risk of cancer. Data on non-LPD malignancies (solid tumors) in pediatric renal transplant recipients are limited. We performed a cohort study using the NAPRTCS transplant registry to describe the incidence of non-LPD malignancy compared with the general pediatric population. The observed incidence rate of non-LPD malignancy in the NAPRTCS transplant registry was 72.1 per 100,000 person-years (SIR 6.7; 95% CI, 5.3, 8.5); a 6.7-fold increased risk compared with the general pediatric population (10.7 cases per 100,000 person-years). Non-LPD malignancy was diagnosed in 35 subjects at a median of 726 days post-transplant. The most common type of malignancy was renal cell carcinoma. The increased risk of non-LPD malignancy was seen in all patients regardless of age, gender, race, etiology of end-stage kidney disease, and transplant era. The specific type of immunosuppression was not identified as a risk factor. In this first large-scale study of North American pediatric renal transplant recipients, we observed a 6.7-fold increased risk of non-LPD malignancy compared with the general pediatric population. Further examination of this unique patient population may provide greater insight into the impact of transplant and immunosuppression on malignancy risk.

Immune profile of pediatric renal transplant recipients following alemtuzumab induction.

The incidence of developing circulating anti-human leukocyte antigen antibodies and the kinetics of T cell depletion and recovery among pediatric renal transplant recipients who receive alemtuzumab induction therapy are unknown. In a collaborative endeavor to minimize maintenance immunosuppression in pediatric renal transplant recipients, we enrolled 35 participants from four centers and treated them with alemtuzumab induction therapy and a steroid-free, calcineurin-inhibitor-withdrawal maintenance regimen. At 3 months after transplant, there was greater depletion of CD4(+) than CD8(+) T cells within the total, naive, memory, and effector memory subsets, although depletion of the central memory subset was similar for CD4(+) and CD8(+) cells. Although CD8(+) T cells recovered faster than CD4(+) subsets overall, they failed to return to pretransplant levels by 24 months after transplant. There was no evidence for greater recovery of either CD4(+) or CD8(+) memory cells than naïve cells. Alemtuzumab relatively spared CD4(+)CD25(+)FoxP3(+) regulatory T cells, resulting in a rise in their numbers relative to total CD4(+) cells and a ratio that remained at least at pretransplant levels throughout the study period. Seven participants (20%) developed anti-human leukocyte antigen antibodies without adversely affecting allograft function or histology on 2-year biopsies. Long-term follow-up is underway to assess the potential benefits of this regimen in children.

Subsets of human CD4(+) regulatory T cells express the peripheral homing receptor CXCR3.

Regulatory T cells (Tregs) migrate into peripheral sites of inflammation such as allografts undergoing rejection, where they serve to suppress the immune response. In this study, we find that ∼30-40% of human CD25(hi) FOXP3(+) CD4(+) Tregs express the peripheral CXC chemokine receptor 3 (CXCR3) and that this subset has potent immunoregulatory properties. Consistently, we observed that proliferative responses as well as IFN-γ production were significantly higher using CXCR3-depleted versus undepleted responders in the mixed lymphocyte reaction, as well as following mitogen-dependent activation of T cells. Using microfluidics, we also found that CXCR3 was functional on CXCR3(pos) Tregs, in as much as chemotaxis and directional persistence towards interferon-γ-inducible protein of 10 kDa (IP-10) was significantly greater for CXCR3(pos) than CXCR3(neg) Tregs. Following activation, CXCR3-expressing CD4(+) Tregs were maintained in vitro in cell culture in the presence of the mammalian target of rapamycin (mTOR) inhibitor rapamycin, and we detected higher numbers of circulating CXCR3(+) FOXP3(+) T cells in adult and pediatric recipients of renal transplants who were treated with mTOR-inhibitor immunosuppressive therapy. Collectively, these results demonstrate that the peripheral homing receptor CXCR3 is expressed on subset(s) of circulating human Tregs and suggest a role for CXCR3 in their recruitment into peripheral sites of inflammation.

Combined en bloc liver-double kidney transplantation in an infant with IVC thrombosis.

We report a case of a pediatric en bloc liver-double kidney transplant in a patient with IVC thrombosis below the renal veins. The patient is an 11-month-old girl diagnosed with congenital nephrotic syndrome at two months of age. Multifocal liver masses were identified on routine ultrasound at eight months of age. Alpha fetoprotein level was 55 319. Biopsy confirmed hepatoblastoma. CT scan confirmed multiple lesions in both lobes, which would require liver transplantation for resection. She was also found to have thrombosis of her infrarenal IVC secondary to multiple central lines. She was listed for combined liver-kidney transplant and began chemotherapy. After four cycles of chemotherapy, she underwent bilateral nephrectomies followed by a combined en bloc liver-double kidney transplant from a size matched donor. In order to provide adequate venous outflow from the kidneys in the absence of a recipient infrarenal IVC, the donor liver and kidneys were procured en bloc with a common arterial inflow via the infrarenal aorta and common outflow via the suprahepatic IVC. Kidney transplantation in the absence of adequate recipient venous drainage may require unusual vascular reconstruction techniques. This case demonstrates a novel approach in patients who may require combined liver-kidney transplantation.

Pre-transplant risk factors for chronic renal dysfunction after pediatric heart transplantation: a 10-year national cohort study.

BACKGROUND: Chronic renal dysfunction may develop after pediatric heart transplantation (PHTx). We examined the incidence of end-stage renal disease (ESRD) and chronic renal insufficiency (CRI) after PHTx, the associated pre-transplant patient characteristics, and impact of renal disease on survival. METHODS: Data sources included the Scientific Registry of Transplant Recipients, Centers for Medicare and Medicaid Services and the Social Security Death Master File. All PHTx recipients (age <18 years) in the USA from 1990 to 1999 who survived >1 year were included. ESRD was defined as long-term dialysis and/or kidney transplant. CRI was defined as creatinine >2.5 mg/dl, including those with ESRD. Relationships between pre-transplant characteristics and time to ESRD and CRI were analyzed using Cox proportional hazards models. The effect of renal disease on survival was analyzed using time-dependent Cox models. RESULTS: During the mean follow-up of 7 years (range 1 to 14 years), 61 of 2,032 (3%) PHTxs developed ESRD. Ten-year actuarial risks for ESRD and CRI were 4.3% and 11.8%, respectively. In a multivariate analysis, significant risk factors for ESRD were: hypertrophic cardiomyopathy; African-American race; intensive care unit (ICU) stay or extracorporeal membrane oxygenation (ECMO) at time of transplant; and pre-transplant diabetes. Risk factors for CRI were: pre-transplant dialysis; hypertrophic cardiomyopathy; African-American race; and previous transplant. Adjusted risk of death in those who developed CRI was 9-fold higher than in those who did not (p < 0.0001). CONCLUSIONS: After PHTx there is an increasing risk for CRI and ESRD over time. Recipients with the characteristics identified in this study may be at greater risk. Development of renal disease significantly increases the risk of post-transplant mortality.

Sirolimus pharmacokinetics in pediatric renal transplant recipients receiving calcineurin inhibitor co-therapy.

We have previously reported sirolimus (SRL) pharmacokinetics (PK) in pediatric renal transplant recipients on a calcineurin inhibitor (CNI)-free protocol. We now report pediatric SRL PK in pediatric renal transplant patients receiving SRL + CNI. SRL was dosed to achieve target trough levels between 10 and 20 ng/mL. We performed 49 SRL PK profiles in pediatric renal transplant recipients receiving SRL in combination with either cyclosporine (CsA; 25 profiles), or tacrolimus (TCL; 24 profiles). Ten of the SRL + TCL profiles were obtained from children receiving SRL on a b.i.d. dosing regimen. All other SRL profiles were q.d. regimens. We calculated, the maximum concentration (C(max)), AUC, apparent clearance (aCL; dose/AUC) for dose in mg/m(2), and mean residence time (MRT). SRL levels were measured at 6 and 7 time points for b.i.d. and q.d. dosing, respectively. Regression analysis of SRL trough values vs. AUC showed good correlation in the SRL q.d. + CsA, SRL q.d. + TCL, and SRL b.i.d. + TCL groups (r(2) = 0.95, 0.68, and 0.44, respectively). SRL aCL corrected for body surface area was higher in children aged 0-5 yr receiving SRL with either CsA or TCL. SRL dosing schedule should be tailored to each patient. Higher SRL aCL may be present in younger children when administered with CNI.

A randomized multicenter trial of OKT3 mAbs induction compared with intravenous cyclosporine in pediatric renal transplantation.

Acute rejection leading to renal graft failure is more frequent among children. In patients treated with T cell antibody induction, retrospective data from the pediatric registry show a 22% reduction in the risk of graft failure. We conducted a randomized trial (n = 287) using OKT3 mAbs in one (OKT3) arm and intravenous cyclosporine in the other arm (CYS). Maintenance therapy consisted of randomized, double blind Sandimmune or Neoral together with prednisone and either azathioprine (AZA) or mycophenolate mofetil (MMF). Morbidity, mortality, rejection rates and adverse reactions in the two study arms were similar. Through 4 yr, graft failure was 27% in OKT3 and 19% in CYS (p = 0.15). One-year graft survival was 89.1% in OKT3 and 89.2% in CYS (p = .19). In multivariate analysis, OKT3 had a numerically inferior graft survival (RR = 1.4, CI 0.8-2.2, p = 0.22). In OKT3 graft survival was inferior for children aged 6 yr or younger. Our trial demonstrates that the incidence of acute rejection or graft failure in pediatric patients is not improved by OKT3 induction therapy relative to cyclosporine induction.

Outcome of renal transplantation for Wilms' tumor and Denys-Drash syndrome: a report of the North American Pediatric Renal Transplant Cooperative Study.

In some children with bilateral Wilms' tumor, reduction of tumor burden cannot be accomplished without total nephrectomy. In Denys-Drash syndrome, nephrectomy is required for associated Wilms' tumor or after progression to end stage renal disease secondary to diffuse mesangial sclerosis because of risk of development of Wilms' tumor. Current recommendation is to wait at least 1-2 yr after completion of chemotherapy for Wilms' tumor before renal transplantation. The North American Pediatric Renal Transplant Cooperative Study dialysis (1992-2001) and transplant registries (1987-2002) were analyzed, comparing children 0-18 yr old with Wilms' tumor and Denys-Drash syndrome to other primary diagnoses. There were 37 children with Wilms' tumor and 33 with Denys-Drash syndrome in the dialysis registry. Of these, 10 children with Wilms' tumor and three with Denys-Drash syndrome did not receive a renal transplant and all died. The cause of death was Wilms' tumor in eight children with Wilms' tumor and in one with Denys-Drash syndrome. The transplant registry included 43 children with Wilms' tumor, 43 children with Denys-Drash syndrome, and 7469 patients with other diagnoses. Acute rejection, graft and patient survival profiles from all three groups at 6 months, 1 and 3 yr post-transplant were comparable. There were no graft failures or deaths because of recurrent Wilms' tumor in the Drash group. There was one death with Wilms' tumor in the Wilms' group - a 2.5-yr-old child transplanted after 6 months of dialysis who died of Wilms' <6 months after renal transplantation. In conclusion, most children dialyzed because of Wilms' tumor and Denys-Drash syndrome who did not receive a renal transplant died of Wilms' tumor. However, the outcomes of children with Wilms' tumor and Denys-Drash syndrome who proceeded to renal transplantation are comparable with children with other diagnoses, with no graft failures because of recurrence and only one death from Wilms' tumor in a Wilms' patient who received only a short course of dialysis prior to transplantation. Current practices in children with Wilms' tumor and Denys-Drash syndrome appear to be on target to portend good outcome following renal transplantation.

Pediatric transplantation, 1994-2003.

This article uses OPTN/SRTR data to review trends in pediatric transplantation over the last decade. In 2003, children younger than 18 made up 3% of the 82,885 candidates for organ transplantation and 7% of the 25,469 organ transplant recipients. Children accounted for 14% of the 6,455 deceased organ donors. Pediatric organ transplant recipients differ from their adult counterparts in several important aspects, including the underlying etiology of organ failure, the complexity of the surgical procedures, the pharmacokinetic properties of common immunosuppressants, the immune response following transplantation, the number and degree of comorbid conditions, and the susceptibility to post-transplant complications, especially infectious diseases. Specialized pediatric organ transplant programs have been developed to address these special problems. The transplant community has responded to the particular needs of children and has provided them special consideration in the allocation of deceased donor organs. As a result of these programs and protocols, children are now frequently the most successful recipients of organ transplantation; their outcomes following kidney, liver, and heart transplantation rank among the best. This article demonstrates that substantial improvement is needed in several areas: adolescent outcomes, outcomes following intestine transplants, and waiting list mortality among pediatric heart and lung candidates.

Pediatric transplantation.

Analysis of the OPTN/SRTR database demonstrates that, in 2002, pediatric recipients accounted for 7% of all recipients, while pediatric individuals accounted for 14% of deceased organ donors. For children fortunate enough to receive a transplant, there has been continued improvement in outcomes following all forms of transplantation. Current 1-year graft survival is generally excellent, with survival rates following transplantation in many cases equaling or exceeding those of all other recipients. In renal transplantation, despite excellent early graft survival, there is evidence that long-term graft survival for adolescent recipients is well below that of other recipients. A causative role for noncompliance is possible. While the significant improvements in graft and patient survival are laudable, waiting list mortality remains excessive. Pediatric candidates awaiting liver, intestine, and thoracic transplantation face mortality rates generally greater than those of their adult counterparts. This finding is particularly pronounced in patients aged 5 years and younger. While mortality awaiting transplantation is an important consideration in refining organ allocation strategies, it is important to realize that other issues, in addition to mortality, are critical for children. Consideration of the impact of end-stage organ disease on growth and development is often equally important, both while awaiting and after transplantation.

Post-transplant infections now exceed acute rejection as cause for hospitalization: a report of the NAPRTCS.

Newer immunosuppressive agents have dramatically reduced the rates of acute graft rejection (AR) over the last decade but may have exacerbated the problem of post-transplant infections (PTI). We analyzed data from the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) to determine the risks of hospitalization from PTI vs. AR in the years 1987-2000. For patients transplanted in 1987, the AR-associated hospitalization rate exceeded the equivalent hospitalization rate for PTI at both early (1-6 months) and later time points (6-24 months). In contrast, for patients transplanted in the year 2000, the PTI-associated hospitalization rate was twice that for AR-associated hospitalization during each time period. During the first two years post-transplant, rates of AR hospitalization trended significantly downwards (p < 0.001) while rates of PTI-associated hospitalization stayed constant. In the 6-24-month time period post-transplant, the risk of bacterial and viral infection-related hospitalization rose significantly from 1987 to 2000 (p < 0.001 for trend by transplant year). We conclude that the causes of hospitalization at all times up to 24 months post-transplant, including the critical early 6 months, have shifted away from AR to PTI.

The report of a national conference on the wait list for kidney transplantation.

In March, 2002, over 100 members of the transplant community assembled in Philadelphia for a meeting designed to address problems associated with the growing number of patients seeking kidney transplantation and added to the waiting list each year. The meeting included representatives of nine US organizations with interests in these issues. Participants divided into work groups addressing access to the waiting list, assigning priority on the list, list management, and identifying appropriate candidates for expanded criteria donor kidneys. Each work group outlined problems and potential remedies within each area. This report summarized the issues and recommendations regarding the waiting list for kidney transplantation addressed in the Philadelphia meeting.

Pretransplant peritoneal dialysis and graft thrombosis following pediatric kidney transplantation: a NAPRTCS report.

Graft thrombosis is a common cause of graft failure in pediatric renal transplantation. Several previous studies, including a North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) review of pretransplant dialysis status and graft outcomes, have described a potential correlation of peritoneal dialysis (PD) and graft thrombosis. This issue is of particular concern for pediatric transplant programs as more than 65% of children with end stage renal disease are treated with PD. We reviewed 7247 pediatric renal transplants performed between 1987 and 2001. Thrombosis was the cause of graft loss in 2.7% (199) of all the transplants performed. Among failed transplants, thrombosis was the third most common cause of graft loss in both index (11.6%) and subsequent transplants (14.5%). Thrombosis becomes the most common cause of graft failure (21%, 61/294) if one looks at transplants in the later cohort, from 1996 to 2001. This change is primarily because of a decrease in the incidence of acute rejection. In the PD group, 3.4% of all grafts were lost as a result of thrombosis. This compares with 1.9% in the hemodialysis group, 2.4% in the pre-emptive transplant group, and 4.1% among patients who received both dialysis modalities. There was a statistically significant difference in thrombosis failure risk in the different dialysis groups (p = 0.005) with those who received only peritoneal dialysis having the highest risk. Additional significant risk factors for graft thrombosis included; cadaver donor source (p < 0.001), cold ischemia time >24 h (p < 0.001), history of prior transplant (p < 0.001), donor age <6 yr (p < 0.001), and >5 pretransplant blood transfusions (p = 0.02). Using stepwise proportional hazards modeling, only pretransplant peritoneal dialysis, >24 h cold ischemia time, prior transplant, and donor age <6 yr were simultaneously associated with an increased risk of thrombosis. We conclude that pretransplant PD is associated with an increased risk of graft thrombosis. Special precautions should be undertaken in pediatric renal transplant patients who have received PD, especially infants and young children.

Regulatory CD25+ T cells in human kidney transplant recipients.

Recent evidence suggests that a population of professional regulatory cells, which limit immune responsiveness, exist in rodents and healthy human subjects. However, their role in disease states remains unclear. A proportion of renal transplant recipients do not demonstrate in vitro reactivity toward their mismatched donor-derived HLA-DR antigens; it was therefore hypothesized that this may be due to such regulatory cells. A cohort of 23 renal transplant recipients was studied at a single institution. In patients with no history of acute rejection, 6 (40%) of 15 demonstrated regulation toward the mismatched HLA-DR allopeptides by CD25(+) cells. By contrast, only one (12.5%) in eight of those with a history of acute rejection demonstrated regulation. Interestingly, if the patient assays were stratified according to initial in vitro immune responsiveness toward the mismatched allopeptides, 8 (47.1%) of 17 of patient assays with low allopeptide responsiveness (alloreactive T cell frequencies less than 60/million) demonstrated regulation of indirect pathway alloresponses by CD25(+) cells, whereas 0 of 8 with higher responses (frequencies greater than 60/million) demonstrated no such regulation (P < 0.05 by chi(2) test). The regulatory cells are present in the circulation as early as 3 mo after transplantation and persist for a number of years, despite conventional immunosuppression. Furthermore, induction treatment with anti-IL-2R mAb did not prevent the development of these regulatory CD25(+) cells. Data from two patients suggest that these cells may also play a role in preventing epitope shifting, implicated in the ongoing immune activation contributing to chronic rejection, and that loss of regulation in a given patient may precede an episode of rejection.