18F-FDG PET/CT in patients with post-transplant lymphoproliferative disorders: so far so good

Abstract

Post-transplant lymphoproliferative disorders (PTLD) are a heterogeneous group of lymphoproliferative diseases occurring after solid organ transplant (SOT) or allogeneic hematopoietic cell transplant (HCT). Epstein-Barr virus (EBV) serologymismatch among recipient and donor, type of transplanted organ, and intensity and type of immunosuppression are considered as established risk factors for developing PTLD. The risk is also higher among children compared with adults [1]. According to the recent update of the WHO classification of tumors of hematopoietic and lymphoid tissues, PTLD are classified in early lesions (non-destructive PTLD), monomorphic PTLD (B cell, T cell, and NK cell subtype), polymorphic PTLD, and classical Hodgkin lymphoma PTLD. Monomorphic PTLD (in particular diffuse large B cell lymphoma) is the most frequent PTLD subtype [2]. Notably, PTLD is characterized by a high incidence of extranodal disease [1]. As PTLD are serious post-transplant complications associated with significant morbidity and mortality, a timely and accurate diagnosis of these disorders is needed. The diagnosis of PTLD can be challenging due to the nonspecific clinical presentation and heterogeneity in histopathologic and immunophenotypic presentation; therefore, histopathology and adequate immunophenotyping are essential to confirm the diagnosis of PTLD [1]. About the imaging methods, current Nat ional Comprehensive Cancer Network (NCCN) guidelines recommend chest/abdomen/pelvis contrast-enhanced computed tomography (CECT) and/or whole-body fluorine-18 fluorodeoxyglucose positron emission tomography/ computed tomography (F-FDG PET/CT) as part of initial diagnostic workup for PTLD [3]. According to the recent evidence-based guidelines from the American Society of Transplantation, F-FDG PET/CT may provide additional useful information for staging and end of treatment response assessment in adults and children with PTLD [4]. The article of Montes de Jesus et al. recently published in EJNMMI provides further evidence on the usefulness of FFDG PET/CT in the management of patients with PTLD [5]. In this retrospective study, the authors evaluated the diagnostic performance of F-FDG PET/CT in a significant population (n = 91) of patients with suspected PTLD examining the factors affecting the diagnostic yield of F-FDG PET/CT. Sensitivity, specificity, positive and negative predictive value, and accuracy of F-FDG PET/CT for the diagnosis of PTLD were 85%, 90%, 83%, 92%, and 89%, respectively, with good interobserver agreement (k = 0.78). Among the main clinical features, only increased lactate dehydrogenase levels seemed to be correlated with a true positive F-FDG PET/CT scan in PTLD patients. EBV-DNA load and timing of F-FDG PET/CT after transplantation did not affect the diagnostic performance of FFDG PET/CT in PTLD [5]. The good diagnostic performance reported in this study suggests that F-FDG PET/CT is a valuable imaging modality for detecting PTLD. These findings are in agreement with the results of previous published studies on the same topic [6–8] that, however, presented a different methodology compared to the study of Montes de Jesus et al. This article is part of the Topical Collection on Hematology