Combined Visual and Semiquantitative Evaluation Improves Outcome Prediction by Early Midtreatment 18F-FDG PET in Diffuse Large B-Cell Lymphoma.

The purpose of this study was to assess the predictive and prognostic value of interim FDG PET (iPET) in evaluating early response to immunochemotherapy after 2 cycles (PET-2) in diffuse large B-cell lymphoma (DLBCL) by applying 2 different methods of interpretation: the Deauville visual 5-point scale (5-PS) and a change in SUV (ΔSUV) by semiquantitative evaluation. Methods: In total, 145 patients with newly diagnosed DLBCL underwent pretreatment PET and PET-2 assessment. PET-2 was classified according to both 5-PS and percentage ΔSUV. Receiver-operating-characteristic analysis was performed to compare the accuracy of the 2 methods for predicting progression-free survival. Survival estimates, based on each method separately and combined, were calculated for iPET-positive (iPET+) and iPET-negative (iPET-) groups and compared. Results: Both with 5-PS and with ΔSUV-based evaluations, significant differences were found between the progression-free survival of iPET- and iPET+ patient groups (P < 0.001). Visually, the best negative predictive value (NPV) and positive predictive value (PPV) occurred when iPET was defined as positive if the Deauville score was 4-5 (89% and 59%, respectively). Using the 66% ΔSUV cutoff reported previously, NPV and PPV were 80% and 76%, respectively. ΔSUV at the 48.9% cutoff, reported for the first time here, produced 100% specificity along with the highest sensitivity (24%). The 5-PS and a semiquantitative ΔSUV of less than 48.9% for each PET-2 gave the same PET-2 classification (positive or negative) in 70% (102/145) of all patients. This combined classification delivered NPV and PPV of 89% and 100%, respectively, and all iPET+ patients failed to achieve or remain in remission. Conclusion: In this large consistently treated and assessed series of DLBCL patients, iPET had good prognostic value interpreted either visually or semiquantitatively. We determined that the most effective ΔSUV cutoff was 48.9% and that when combined with 5-PS assessment, a positive PET-2 result was highly predictive of treatment failure.

Paediatric and adolescent Hodgkin lymphoma: information derived from diffuse organ uptake of 18 F-fluorodeoxyglucose on pre-treatment and on interim PET/CT.

PURPOSE: To evaluate, in children with Hodgkin lymphoma (HL), the frequency and intensity of visually diffuse FDG uptake by selected organs at baseline (bPET) and on interim PET/CT (iPET), and to evaluate the relation between FDG uptake, metabolic response and evolution of the disease with treatment. PATIENTS AND METHODS: Thirty children with HL had bPET and then iPET after two cycles of treatment, which were blind-read retrospectively. Excluding sites with focal uptake, diffuse FDG uptake by thymus, bone marrow at iliac crests, liver, spleen, and the spinal cord at the 12th thoracic vertebra (Th12) was evaluated visually using a three-point scoring method and semiquantitatively by measuring SUVmax. Visualisation of activated brown adipose tissue (BAT) was also quoted. Five children had refractory HL. Recurrence-free survival was determined for each patient. Nine patients relapsed; in 21 non-relapsing patients, the median follow-up period was 43 months (range: 28-61). RESULTS: On bPET, the rate of diffuse and intense (visual score = 3) FDG uptake was 48 % in the spleen, 43 % in the spinal cord at Th12, 37 % in bone marrow, 21 % in the thymus and 7 % in BAT. At least one of those sites showed diffuse and intense FDG uptake in 77 % of patients. On iPET, a significant decrease in SUVmax was observed in thymus, iliac crest bone marrow and spleen, but not in spinal cord. In contrast, the FDG uptake by the liver significantly increased. The absence of SUVmax increase in the liver between bPET and iPET was the best criterion to predict a refractory disease (PPV = 55 %, NPV = 100 %). Its area under ROC (AUC) was 0.9 vs. 0.73 for five-point Deauville criteria. For prediction of relapse, two criteria were derived from the evolution of diffuse uptake between bPET and iPET: no increase in liver uptake and an increase > 5 % in spinal cord uptake. As compared with 13 patients who matched none of those criteria, the hazard ratio (HR) for relapse was 2.1 in 13 patients who matched one criterion, and 10.3 in four patients who matched both (Kaplan-Meier analysis p = 0.005). CONCLUSION: Diffuse and intense FDG uptake by organs is frequent in children with HL on bPET. On iPET, it is frequently reduced in all sites except the liver, which may pose problems for visual quotation of the FDG intensity of HL foci. The variation of SUVmax between bPET and iPET permitted us to achieve a prediction of refractory or relapsing HL that was at least as effective as using criteria based on FDG uptake by the HL lesions. The results of this retrospective pilot study need further validation.