The Accuracy of PET in the Detection of Posttransplant Lymphoproliferative Disorder (PTLD)

PET scan has emerged as a powerful tool in the diagnosis and staging of both Hodgkin and different subtypes of aggressive non-Hodgkin lymphoma. We investigated the accuracy of PET scan in 170 patients with suspected posttransplant lymphoproliferative disorder (PTLD).

We retrospectively reviewed all patients in our center between 2003 and 2010 for whom a PET-scan was requested for the indication PTLD. 170 PET-scans in 150 patients were eligible for evaluation. In 45 cases, the patient had already a biopsy proven PTLD before PET-scanning and PET was considered a staging tool in these patients. In the remaining 125 PET-scans, PLTD was only suspected at the time PET was performed. In 73 (43%) and 97 (57%) cases PET scan without CT and combined PET/CT scan were ordered respectively. Because the aim of this study was to determine the accuracy of PET scan in diagnosis of PTLD, we evaluated only results of the PET scans. PET-scans were blindly scored on a four-point scale. Results were compared with biopsy as the gold standard.

The majority of PET scans were performed in kidney transplant recipients (35%), followed by liver (15%), lung (15%), heart (15%), hematopoietic stem cell (15%), combined (5%) and bowel (1%) transplantation. In 119 (70%) patients a biopsy was available. We found a sensitivity of PET of 89%, specificity of 89%, positive predictive value (PPV) of 91% and negative predictive value (NPV) of 87%. In a subanalysis of the 125 scans performed for differential diagnosis PTLD versus other diseases, sensitivity, specificity, PPV and NPV were 90%, 89%, 85% and 93% respectively. FDG-uptake in PTLD was generally high with a median mean and maximal standardized uptake value (SUV) of 9.0 and 17.4. False positive results were mainly due to infectious or inflammatory conditions, whereas false negative results were mainly reported in limited stage PTLD. Atypical extrandodal presentation was a frequent finding including diffuse pulmonary involvement and gastro-intestinal lesions.

From these data, we can conclude that PET is highly sensitive for the detection of lesions of PTLD, and that PET has an excellent ability to differentiate PTLD from other diseases.

No relevant conflicts of interest to declare.