Optimization of universal allogeneic CAR-T cells combining CRISPR and transposon-based technologies for treatment of acute myeloid leukemia.

Despite the potential of CAR-T therapies for hematological malignancies, their efficacy in patients with relapse and refractory Acute Myeloid Leukemia has been limited. The aim of our study has been to develop and manufacture a CAR-T cell product that addresses some of the current limitations. We initially compared the phenotype of T cells from AML patients and healthy young and elderly controls. This analysis showed that T cells from AML patients displayed a predominantly effector phenotype, with increased expression of activation (CD69 and HLA-DR) and exhaustion markers (PD1 and LAG3), in contrast to the enriched memory phenotype observed in healthy donors. This differentiated and more exhausted phenotype was also observed, and corroborated by transcriptomic analyses, in CAR-T cells from AML patients engineered with an optimized CAR construct targeting CD33, resulting in a decreased in vivo antitumoral efficacy evaluated in xenograft AML models. To overcome some of these limitations we have combined CRISPR-based genome editing technologies with virus-free gene-transfer strategies using Sleeping Beauty transposons, to generate CAR-T cells depleted of HLA-I and TCR complexes (HLA-IKO/TCRKO CAR-T cells) for allogeneic approaches. Our optimized protocol allows one-step generation of edited CAR-T cells that show a similar phenotypic profile to non-edited CAR-T cells, with equivalent in vitro and in vivo antitumoral efficacy. Moreover, genomic analysis of edited CAR-T cells revealed a safe integration profile of the vector, with no preferences for specific genomic regions, with highly specific editing of the HLA-I and TCR, without significant off-target sites. Finally, the production of edited CAR-T cells at a larger scale allowed the generation and selection of enough HLA-IKO/TCRKO CAR-T cells that would be compatible with clinical applications. In summary, our results demonstrate that CAR-T cells from AML patients, although functional, present phenotypic and functional features that could compromise their antitumoral efficacy, compared to CAR-T cells from healthy donors. The combination of CRISPR technologies with transposon-based delivery strategies allows the generation of HLA-IKO/TCRKO CAR-T cells, compatible with allogeneic approaches, that would represent a promising option for AML treatment.

Treosulfan-Based Conditioning Regimen In Pediatric Hematopoietic Stem Cell Transplantation: A Retrospective Analysis on Behalf of the Spanish Group for Hematopoietic Transplantation and Cellular Therapy (GETH-TC).

Increasing data on treosulfan-based conditioning regimens before hematopoietic stem cell transplantation (HSCT) demonstrate the consistent benefits of this approach, particularly regarding acute toxicity. This study aimed to describe the results of treosulfan-based conditioning regimens in children, focusing on toxicity and outcomes when used to treat both malignant and nonmalignant diseases. This retrospective observational study of pediatric patients treated in Spain with treosulfan-based conditioning regimens before HSCT was based on data collection from electronic clinical records. We studied a total of 160 treosulfan-based conditioning HSCTs to treat nonmalignant diseases (n = 117) or malignant diseases (n = 43) in 158 children and adolescents. The median patient age at HSCT was 5.1 years (interquartile range, 2 to 10 years). The most frequent diagnoses were primary immunodeficiency (n = 42; 36%) and sickle cell disease (n = 42; 36%) in the nonmalignant disease cohort and acute lymphoblastic leukemia (n = 15; 35%) in the malignant disease cohort. Engraftment occurred in 97% of the patients. The median times to neutrophil engraftment (17 days versus 14 days; P = .008) and platelet engraftment (20 days versus 15 days; P = .002) were linger in the nonmalignant cohort. The 1-year cumulative incidence of veno-occlusive disease was 7.98% (95% confidence interval [CI], 4.6% to 13.6%), with no significant differences between cohorts. The 1-year cumulative incidence of grade III-IV acute graft-versus-host disease (GVHD) was higher in the malignant disease cohort (18% versus 3.2%; P = .011). Overall, the malignant cohort had both a higher total incidence (9% versus 3%; P < .001) and a higher 2-year cumulative incidence (16% versus 1.9%; P < .001) of total chronic GVHD. The 2-year cumulative transplantation-related mortality was 15%, with no difference between the 2 cohorts. The 5-year overall survival was 80% (95% CI, 72% to 86%) and was higher in the nonmalignant cohort (87% versus 61%; P = .01). The 2-year cumulative incidence of relapse was 25% in the malignant cohort. The 5-year cumulative GVHD-free, relapse-free survival rate was 60% (95% CI, 51% to 70%) and was higher in the nonmalignant cohort (72% versus 22%; P < .001). A treosulfan-based radiation-free conditioning regimen is feasible, achieving a high engraftment rate and 5-year overall survival, and is an emerging option for the first HSCT in nonmalignant diseases.

The bone marrow niche regulates redox and energy balance in MLL::AF9 leukemia stem cells.

Eradicating leukemia requires a deep understanding of the interaction between leukemic cells and their protective microenvironment. The CXCL12/CXCR4 axis has been postulated as a critical pathway dictating leukemia stem cell (LSC) chemoresistance in AML due to its role in controlling cellular egress from the marrow. Nevertheless, the cellular source of CXCL12 in the acute myeloid leukemia (AML) microenvironment and the mechanism by which CXCL12 exerts its protective role in vivo remain unresolved. Here, we show that CXCL12 produced by Prx1+ mesenchymal cells but not by mature osteolineage cells provide the necessary cues for the maintenance of LSCs in the marrow of an MLL::AF9-induced AML model. Prx1+ cells promote survival of LSCs by modulating energy metabolism and the REDOX balance in LSCs. Deletion of Cxcl12 leads to the accumulation of reactive oxygen species and DNA damage in LSCs, impairing their ability to perpetuate leukemia in transplantation experiments, a defect that can be attenuated by antioxidant therapy. Importantly, our data suggest that this phenomenon appears to be conserved in human patients. Hence, we have identified Prx1+ mesenchymal cells as an integral part of the complex niche-AML metabolic intertwining, pointing towards CXCL12/CXCR4 as a target to eradicate parenchymal LSCs in AML.

Outcomes of Unmanipulated Haploidentical Transplantation Using Post-Transplant Cyclophosphamide (PT-Cy) in Pediatric Patients With Acute Lymphoblastic Leukemia.

HLA-haploidentical transplantation (haplo-HCT) using post-transplantation-cyclophosphamide (PT-Cy) is a feasible procedure in children with malignancies. However, large studies on Haplo-HCT with PT-Cy for childhood acute lymphoblastic leukemia (ALL) are lacking. We analyzed haplo-HCT outcomes in 180 children with ALL. Median age was 9 years, and median follow-up was 2.7 years. Disease status was CR1 for 24%, CR2 for 45%, CR+3 for 12%, and active disease for 19%. All patients received PT-Cy day +3 and +4. Bone marrow (BM) was the stem cell source in 115 patients (64%). Cumulative incidence of 42-day engraftment was 88.9%. Cumulative incidence of day-100 acute graft-versus-host disease (GVHD) grade II-IV was 28%, and 2-year chronic GVHD was 21.9%. At 2 years, cumulative incidence of nonrelapse mortality (NRM) was 19.6%. Cumulative incidence was 41.9% for relapse and 25% for patients in CR1. Estimated 2-year leukemia free survival was 65%, 44%, and 18.8% for patients transplanted in CR1, CR2, CR3+ and 3% at 1 year for active disease. In multivariable analysis for patients in CR1 and CR2, disease status (CR2 [hazard ratio {HR} = 2.19; P = .04]), age at HCT older than 13 (HR = 2.07; P = .03) and use of peripheral blood stem cell (PBSC) (HR = 1.98; P = .04) were independent factors associated with decreased overall survival. Use of PBSC was also associated with higher NRM (HR = 3.13; P = .04). Haplo-HCT with PT-Cy is an option for children with ALL, namely those transplanted in CR1 and CR2. Age and disease status remain the most important factors for outcomes. BM cells as a graft source is associated with improved survival.

Engraftment after autologous hematopoietic stem cell transplantation in patients mobilized with Plerixafor: A retrospective, multicenter study of a large series of patients.

Plerixafor (PLX) appears to effectively enhance hematopoietic stem-cell mobilization prior to autologous hematopoietic stem cell transplantation (auto-HCT). However, the quality of engraftment following auto-HCT has been little explored. Here, engraftment following auto-HCT was assessed in patients mobilized with PLX through a retrospective, multicenter study of 285 consecutive patients. Information on early and 100-day post-transplant engraftment was gathered from the 245 patients that underwent auto-HCT. The median number of PLX days to reach the stem cell collection goal (≥2 × 106 CD34+ cells/kg) was 1 (range 1-4) and the median PLX administration time before apheresis was 11 h (range 1-18). The median number of apheresis sessions to achieve the collection goal was 2 (range 1-5) and the mean number of CD34+ cells collected was 2.95 × 106/kg (range 0-30.5). PLX administration was safe, with only 2 mild and transient gastrointestinal adverse events reported. The median time to achieve an absolute neutrophil count (ANC) >500/µL was 11 days (range 3-31) and the median time to platelet recovery >20 × 103/µL was 13 days (range 5-69). At 100 days after auto-HCT, the platelet count was 137 × 109/L (range 7-340), the ANC was 2.3 × 109/L (range 0.1-13.0), and the hemoglobin concentration was 123 g/L (range 79-165). PLX use allowed auto-HCT to be performed in a high percentage of poorly mobilized patients, resulting in optimal medium-term engraftment in the majority of patients in whom mobilization failed, in this case mainly due to suboptimal peripheral blood CD34+ cell concentration on day +4 or low CD34+ cell yield on apheresis.

Treatment of steroid-refractory chronic graft-versus-host disease with imatinib: Real-life experience of the Spanish group of hematopoietic transplantation (GETH).

Treatment of steroid-refractory chronic graft-versus-host disease (cGVHD) is a challenge. Here, we describe a retrospective analysis of 66 patients with steroid-refractory cGVHD treated with imatinib (starting dose of 100 mg in 70% of patients; maximum dose of 100-200 mg in 74%). Most patients had multi-organ involvement (≥2 organs, 83%), with the most affected being skin (85%), oral mucosa (55%), eyes (42%), and lungs (33%). The overall response rate was 41% (21 partial and three complete responses). The organ with the best response rate was the skin (46%), followed by gastrointestinal tract (43%), liver (41%), the oral mucosa (36%), eyes (29%), and lungs (18%). Imatinib led to steroid tapering in 17/38 patients. Twenty-five (38%) patients experienced imatinib-related adverse events, comprising extra-hematologic toxicity (n = 24, 36%) and hematologic toxicity (n = 6, 9%). No cases of grade 4-5 toxicity were reported. The main causes of imatinib discontinuation were treatment failure (52%) and toxicity (9%). After a median follow-up of 41 months, the 3-year overall survival was 81%, with no difference between imatinib responders and non-responders. These real-life results show that imatinib is safe and has moderate efficacy in patients with heavily pre-treated cutaneous sclerotic cGVHD; however, activity against lung cGVHD is very limited.

Impact of spleen size and splenectomy on outcomes of allogeneic hematopoietic cell transplantation for myelofibrosis: A retrospective analysis by the chronic malignancies working party on behalf of European society for blood and marrow transplantation (EBMT).

The role of spleen size and splenectomy for the prediction of post-allogeneic hematopoietic stem cell transplant (allo-HCT) outcome in myelofibrosis remains under debate. In EBMT registry, we identified a cohort of 1195 myelofibrosis patients transplanted between 2000-2017 after either fludarabine-busulfan or fludarabine-melphalan regimens. Overall, splenectomy was performed in 202 (16.9%) patients and its use decreased over time (28.3% in 2000-2009 vs 14.1% in 2010-2017 period). By multivariate analysis, splenectomy was associated with less NRM (HR 0.64, 95% CI 0.44-0.93, P = .018) but increased risk of relapse (HR 1.43, 95% CI 1.01-2.02, P = .042), with no significant impact on OS (HR 0.86, 95% CI 0.67-1.12, P = .274). However, in subset analysis comparing the impact of splenectomy vs specific spleen sizes, for patients with progressive disease, an improved survival was seen in splenectomised subjects compared to those patients with a palpable spleen length ≥ 15 cm (HR 0.44, 95% CI 0.28-0.69, P < .001), caused by a significant reduction in NRM (HR 0.26, 95% CI 0.14-0.49, P < .001), without significantly increased relapse risk (HR 1.47, 95% CI 0.87-2.49, P = .147). Overall, despite the possible biases typical of retrospective cohorts, this study highlights the potential detrimental effect of massive splenomegaly in transplant outcome and supports the role of splenectomy for myelofibrosis patients with progressive disease and large splenomegaly.

Haematopoietic stem cell transplantation in adult soft-tissue sarcoma: an analysis from the European Society for Blood and Marrow Transplantation.

BACKGROUND: The role of high-dose chemotherapy with autologous stem cell transplantation (ASCT) in the treatment of soft-tissue sarcoma (STS) remains an unsettled issue. Prospective clinical trials failed to prove a benefit of the procedure but were limited by small and heterogeneous patient cohorts. Thus, it is unknown if ASCT may be a valuable treatment option in specific patient subgroups. METHODS: The purpose of this study was to investigate the value of ASCT according to histological subtype in STS patients who were registered in the European Society for Blood and Marrow Transplantation database between 1996 and 2016. RESULTS: Median progression-free (PFS) and overall survival (OS) in the entire cohort of 338 patients were 8.3 and 19.8 months, respectively, and PFS and OS at 5 years were 13% and 25%, respectively. Analysis of outcomes in different subgroups showed that younger age, better remission status before transplantation and melphalan-based preparative regimen were predictive of benefit from ASCT, whereas histology and grading had no statistically significant impact. CONCLUSIONS: Outcomes after ASCT compared favorably to those of recent trials on conventional chemotherapies and targeted therapies in STS, including histology-tailored approaches. ASCT, thus, should be reinvestigated in clinical trials focusing on defined patient subgroups.

A new regulatory mechanism of protein phosphatase 2A activity via SET in acute myeloid leukemia.

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy. Although novel emerging drugs are available, the overall prognosis remains poor and new therapeutic approaches are required. PP2A phosphatase is a key regulator of cell homeostasis and is recurrently inactivated in AML. The anticancer activity of several PP2A-activating drugs (e.g., FTY720) depends on their interaction with the SET oncoprotein, an endogenous PP2A inhibitor that is overexpressed in 30% of AML cases. Elucidation of SET regulatory mechanisms may therefore provide novel targeted therapies for SET-overexpressing AMLs. Here, we show that upregulation of protein kinase p38ß is a common event in AML. We provide evidence that p38ß potentiates SET-mediated PP2A inactivation by two mechanisms: facilitating SET cytoplasmic translocation through CK2 phosphorylation, and directly binding to and stabilizing the SET protein. We demonstrate the importance of this new regulatory mechanism in primary AML cells from patients and in zebrafish xenograft models. Accordingly, combination of the CK2 inhibitor CX-4945, which retains SET in the nucleus, and FTY720, which disrupts the SET-PP2A binding in the cytoplasm, significantly reduces the viability and migration of AML cells. In conclusion, we show that the p38ß/CK2/SET axis represents a new potential therapeutic pathway in AML patients with SET-dependent PP2A inactivation.

Response to Novel Drugs before and after Allogeneic Stem Cell Transplantation in Patients with Relapsed Multiple Myeloma.

Multiple myeloma (MM) remains as an incurable disease and, although allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative approach, most patients ultimately relapse, and their treatment remains challenging. Because allo-HSCT can modify not only the biology of the disease, but also the immune system and the microenvironment, it can potentially enhance the response to rescue therapies. Information on the efficacy and safety of novel drugs in patients relapsing after allo-HSCT is lacking, however. The objectives of this study were to evaluate the efficacy and toxicity of rescue therapies in patients with MM who relapsed after allo-HSCT, as well as to compare their efficacy before and after allo-HSCT. This retrospective multicenter study included 126 consecutive patients with MM who underwent allo-HSCT between 2000 and 2013 at 8 Spanish centers. All patients engrafted. The incidence of grade II-IV acute graft-versus-host disease (GVHD) was 47%, and nonrelapse mortality within the first 100 days post-transplantation was 13%. After a median follow-up of 92 months, overall survival (OS) was 51% at 2 years and 43% at 5 years. The median progression-free survival after allo-HSCT was 7 months, whereas the median OS after relapse was 33 months. Patients relapsing in the first 6 months after transplantation had a dismal prognosis compared with those who relapsed later (median OS, 11 months versus 120 months; P < .001). The absence of chronic GVHD was associated with reduced OS after relapse (hazard ratio, 3.44; P < .001). Most patients responded to rescue therapies, including proteasome inhibitors (PIs; 62%) and immunomodulatory drugs (IMiDs; 77%), with a good toxicity profile. An in-depth evaluation, including the type and intensity of PI- and IMiD-based combinations used before and after allo-HSCT, showed that the overall response rate and duration of response after allo-HSCT were similar to those seen in the pretransplantation period. Patients with MM who relapse after allo-HSCT should be considered candidates for therapy with new drugs, which can achieve similar response rates with similar durability as seen in the pretransplantation period. This pattern does not follow the usual course of the disease outside the transplantation setting, where response rates and time to progression decreases with each consecutive line of treatment.

Adoptive T-cell therapy with CD45RA-depleted donor in the treatment of cytomegalovirus disease in immunocompromised non-transplant patients.

Cytomegalovirus (CMV) infections can induce severe complications in immunosuppressed patients. Currently, ganciclovir represents the preferred treatment option; however, in patients with resistance or toxicity related to ganciclovir, the therapeutic options are limited.Cellular immunity plays an important role in the control of viral infections. Adoptive T-cell therapy can contribute to recovering immunological function in immunosuppressed patients. Selective T-cell depletion targeting CD45RA enhances early T-cell recovery and can represent a salvage therapy. In this study, an immunocompromised non-transplanted patient with CMV disease and toxicity to conventional therapy was successfully treated by adoptive transfer of CD45RA-depleted T-cells.

Epigenomic profiling of myelofibrosis reveals widespread DNA methylation changes in enhancer elements and ZFP36L1 as a potential tumor suppressor gene that is epigenetically regulated.

In this study we interrogated the DNA methylome of myelofibrosis patients using high-density DNA methylation arrays. We detected 35,215 differentially methylated CpG, corresponding to 10,253 genes, between myelofibrosis patients and healthy controls. These changes were present both in primary and secondary myelofibrosis, which showed no differences between them. Remarkably, most differentially methylated CpG were located outside gene promoter regions and showed significant association with enhancer regions. This aberrant enhancer hypermethylation was negatively correlated with the expression of 27 genes in the myelofibrosis cohort. Of these, we focused on the ZFP36L1 gene and validated its decreased expression and enhancer DNA hypermethylation in an independent cohort of patients and myeloid cell-lines. In vitro reporter assay and 5'-azacitidine treatment confirmed the functional relevance of hyper-methylation of ZFP36L1 enhancer. Furthermore, in vitro rescue of ZFP36L1 expression had an impact on cell proliferation and induced apoptosis in SET-2 cell line indicating a possible role of ZFP36L1 as a tumor suppressor gene in myelofibrosis. Collectively, we describe the DNA methylation profile of myelofibrosis, identifying extensive changes in enhancer elements and revealing ZFP36L1 as a novel candidate tumor suppressor gene.

Bendamustine as part of conditioning of autologous stem cell transplantation in patients with aggressive lymphoma: a phase 2 study from the GELTAMO group.

We conducted a phase 2 trial to evaluate the safety and efficacy of bendamustine instead of BCNU (carmustine) in the BEAM (BCNU, etoposide, cytarabine and melphalan) regimen (BendaEAM) as conditioning for autologous stem-cell transplantation (ASCT) in patients with aggressive lymphomas. The primary endpoint was 3-year progression-free survival (PFS). Sixty patients (median age 55 [28-71] years) were included. All patients (except one who died early) engrafted after a median of 11 (9-72) and 14 (4-53) days to achieve neutrophil and platelet counts of >0.5 × 109 /l and >20 × 109 /l, respectively. Non-relapse mortality at 100 days and 1 year were 3.3% and 6.7%, respectively. With a median follow-up of 67 (40-77) months, the estimated 3-year PFS and overall survival (OS) were 58% and 75%, respectively. Patients in partial response at study entry had significantly worse PFS and OS than patients who underwent ASCT in complete metabolic remission, and this was the only prognostic factor associated with both PFS (Relative risk [RR], 0.27 [95% confidence interval {CI} [0.12-0.56]) and OS (RR, 0.40 [95% CI 0.17-0.97]) in the multivariate analysis. BendaEAM conditioning is therefore a feasible and effective regimen in patients with aggressive lymphomas. However, patients not in complete metabolic remission at the time of transplant had poorer survival and so should be considered for alternative treatment strategies.

Tratamiento con células mesenquimales de la enfermedad de injerto contra huésped como complicación de trasplante hepático / Treatment of graft-versus-host disease with mesenchymal cells as a complication of a liver transplantation

Presentamos el caso de un paciente trasplantado hepático (TH) de donante cadáver que desarrolló una enfermedad de injerto contra huésped (EICH) agudo, cuyas manifestaciones fundamentales fueron rash cutáneo, diarrea y pancitopenia. Como parte del tratamiento se administraron células mesenquimales. Hasta la fecha no se han descrito en la literatura casos de EICH post-TH tratados con células mesenquimales. A pesar del tratamiento, no se produjo mejoría en la aplasia ni en la clínica gastrointestinal y el paciente falleció por una infección diseminada

We present the case of a liver transplant (LT) recipient donor who developed graft versus host disease (GVHD). The main features were cutaneous rash, diarrhea and pancytopenia. Mesenchymal cells were administered as part of the treatment. This is the first case of a patient with GVHD after LT reported to date. Despite the treatment, there was no improvement in aplasia or gastrointestinal symptoms and the patient died due to a disseminated infection

Treatment of graft-versus-host disease with mesenchymal cells as a complication of a liver transplantation.

We present the case of a liver transplant (LT) recipient donor who developed graft versus host disease (GVHD). The main features were cutaneous rash, diarrhea and pancytopenia. Mesenchymal cells were administered as part of the treatment. This is the first case of a patient with GVHD after LT reported to date. Despite the treatment, there was no improvement in aplasia or gastrointestinal symptoms and the patient died due to a disseminated infection.

Efficacy of the Combination of Immunoadsorption and Rituximab for Treatment in a Case of Severe Focal and Segmental Glomerulosclerosis Recurrence after Renal Transplantation.

BACKGROUND/AIMS: We present a case of a male patient with severe recurrence of focal and segmental glomerulosclerosis (FSGS) after transplant. METHODS: Before the transplant he was treated with plasma exchange. Massive proteinuria was detected post-transplantation and plasma exchanges were performed without response. We administered 5 doses of Rituximab (375 mg/m2) and partial remission was achieved. Proteinuria relapse occurred 1 year post-transplant, so Immunoadsorption (IA) was started instead of plasma exchange with reduction of proteinuria. Later, 2 new episodes of proteinuria relapse were detected and treated by increasing the number of IA sessions and administering new cycles of Rituximab. After achieving partial remission, IA was reduced to one session every 7-10 days as maintenance therapy. RESULTS: Despite the fact of the severe recurrence, renal function and proteinuria remain stable over 8 years after the transplantation was performed. CONCLUSION: Combination of maintenance IA and cycles of Rituximab is an effective treatment for aggressive forms of FSGS recurrence after renal transplantation.

First-line use of rituximab correlates with increased overall survival in late post-transplant lymphoproliferative disorders: retrospective, single-centre study.

This retrospective study evaluates the impact of rituximab on PTLD response and survival in a single-centre cohort. PTLD cases between 1984 and 2009, including heart, kidney, liver and lung transplant recipients, were included. Survival was analysed taking into account the type of PTLD (monomorphic vs. polymorphic), EBV infection status, IPI score, Ann Arbor stage and use of rituximab. Among 1335 transplanted patients, 24 developed PTLD. Median age was 54 yr (range 29-69), median time to diagnosis 50 months (range 0-100). PTLD type was predominantly late/monomorphic (79% and 75%), mostly diffuse large B-cell type. Overall response rate (ORR) was 62% (66% rituximab vs. 50% non-rituximab; P = 0.5). R-CHOP-like regimens were used most frequently (72% of patients treated with rituximab). Median overall survival was 64 months (CI 95% 31-96). OS was significantly increased in patients treated with rituximab (P = 0.01; CI 95% rituximab 58-79 months; non-rituximab 1-30 months). Post-transplant immunosuppression regimen had no effect on survival or time to PTLD, except for cyclosporine A (CyA), which associated with increased time to PTLD (P = 0.02). Rituximab was associated with increased survival in our single-centre series, and it should be considered as first-line therapy for PTLD patients. The possible protective effect of CyA for development of PTLD should be prospectively evaluated.