PTLD Visualization by FDG-PET: Improved Detection of Extranodal Localizations and Response Monitoring.

Posttransplant lymphoproliferative disease (PTLD) is a serious complication that may arise after solid organ transplantation. PTLD may involve nodal as well as extranodal sites, with frequent involvement of the allograft and digestive tract. Extranodal localizations of PTLD may not always be visualized with routine conventional diagnostic methods such as computer tomography (CT) or magnetic resonance imaging (MRI). Our aim was to evaluate the value of 2-[18F] fluoro-2-deoxy-D-glucose (FDG)-PET in the staging and treatment evaluation of histologically confirmed PTLD (patient #3 confirmed by ascites cytology) in 10 kidney transplant recipients transplanted between January 2000 and June 2004. At time of PTLD diagnosis patients were fully staged by standard conventional diagnostic methods according to lymphoma protocols, including at least whole body CT scanning and bone marrow biopsy. In addition, whole body-mode PET studies were performed. All patients had their scans prior to therapy. In addition, four had repeated PET-scans during and after therapy. To compare CT with FDG-PET, all scans were re-evaluated (blinded) by a radiologist and an expert in nuclear medicine, respectively. All PET-scans at initial diagnosis could readily be interpreted and showed high FDG uptake in the primary sites of histological confirmed PTLD. This was true for monomorphic as well as polymorphic PTLD. The large majority of other sites of involvement as detected by conventional diagnostic methods at diagnosis were also PET positive. However, additional extranodal sites were detected by FDG-PET not readily visualized by CT scanning (table 1). After treatment with Rituximab, a decline or disappearance of FDG-uptake coincided with clinical response as detected by conventional diagnostic methods. These findings suggest that FDG-PET is suitable in visualization of (different histological subtypes of) PTLD and useful for both staging and response to treatment evaluation. The ability of FDG-PET to visualize extranodal localizations of PTLD, often present but not readily detectable by routine conventional diagnostic methods, is of additional value.