PTLD Visualization by FDG-PET: Improved Detection of Extranodal Localizations and Response Monitoring.
Authors: Bakker Nicolaas A. , Pruim Jan , Van Son Willem J. , Van der Jagt Eric J. , Kluin-Nelemans Hanneke C. , Van Imhoff Gustaaf W. 
Published: April 2020

Abstract
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.
Sites of PTLD involvement at diagnosis: CT and PET compared Patient Site of Biopsy Ann Arbor Stage Diagnosis* PET CT *Disconcordant lesions are bolded, **confirmed by MRI 1 liver IV jugular, supraclavicular, axillar, mediastinum, lung hili, liver , spleen, para-aortal, paracaval, bone marrow spleen, para-aortal, para-caval 2 ascites IV no abnormal foci No abnormalities 3 colon IV multiple foci abdomen ventral No abnormalities 4 cerebrum IE cerebrum cerebrum** 5 pancreas IE pancreas pancreas 6 lymph node jugular IV lymph node jugular , small pelvic, rectum, surrounding allograft small pelvic, right groin 7 lymph node axillar IV jugular, axillar, liver, rectum, bone marrow jugular, axillar, mediastinum, para-caval , 8 stomach IV supraclavicular, infraclavicular, mediastinum, multiple foci retroperitoneal, stomach, multiple foci abdomen supraclavicular, infraclavicular, mediastinum, para-caval, para-aortal, stomach, central abdomen 9 cerebrum IE cerebrum cerebrum** 10 skin left leg IE skin left leg no other sites involved