18F-FDG PET/contrast enhanced CT in the standard follow-up of patients with lymphoma. / 18F-FDG PET/TC con contraste intravenoso en el seguimiento estandarizado de pacientes con linfoma.

AIM: To assess the diagnostic accuracy of 18F-FDG PET/contrast enhanced computed tomography (ceCT) in the detection of asymptomatic recurrences in patients with lymphoma. MATERIAL AND METHODS: Patients with lymphoma and clinical complete remission underwent 18F-FDG PET/ceCT for standard follow-up.18F-FDG PET and ceCT were evaluated blindly by two independent observers, and classified as positive or negative for recurrence. Additionally a combined evaluation of both techniques was performed. The final diagnosis was established by histopathological analysis or a clinical follow-up longer than 6 months. Statistical diagnostic parameters and concordance levels between both diagnostic techniques were calculated. RESULTS: A total of 114 explorations on 90 patients were analyzed. Only 4 patients were diagnosed as asymptomatic recurrence during the follow-up. 18F-FDG PET/ceCT, 18F-FDG PET and ceCT showed an association with the final diagnosis (p=0.002 and χ2=11.96; p<0.001 and χ2=15.60; p=0.001 and χ2=11.96, respectively). The concordance between 18F-FDG PET and ceCT was moderate/high and significant (kappa=0.672; p<0.001). A sensitivity and specificity of 50% and 88% was obtained for the 18F-FDG PET/ceCT civ, 50% and 93% for the 18F-FDG PET, and 50% and 91% for the ceCT. CONCLUSION: The combined use of 18F-FDG PET/ceCT did not offer any advantage compared to any isolated diagnostic technique in the detection of asymptomatic lymphoma recurrence.

Basal (18)F-FDG PET/CT in follicular lymphoma: A comparison of metabolic and clinical variables in the prognostic assessment.

AIM: To analyze the relationship of clinical variables related to prognosis and tumor burden, with metabolic variables obtained in the staging (18)F-FDG PET/CT, and their value in the prognosis in follicular lymphoma (FL). METHODS: 82 patients with FL, a (18)F-FDG PET/CT at diagnosis and a follow-up for a minimum of 12 months, were retrospectively enrolled in the present study. Clinical variables (Tumor grade, Follicular Lymphoma International Prognostic Index (FLIPI) and Tumor burden) were evaluated. Metabolic variables such as SUVmax in the highest hypermetabolic lesion, extralymphatic locations, number of involved lymph node locations, bone marrow (BM) involvement, PET stage and diameter of the biggest hypermetabolic lesion, were analyzed in order to establish a PET score and classify the studies in low, intermediate and high metabolic risk. Clinical and metabolic variables (included metabolic risk) were compared. The relation among all variables and disease-free survival (DFS) was studied. RESULTS: The 28% of patients had a high-grade tumor. The 30.5% had FLIPI risk low, 29.3% intermediate y 40.2% high. The 42.7% presented a high tumor burden. The PET/CT was positive in 94% of patients. The tumor grade did not show significant relation with metabolic variable. FLIPI risk and tumor burden showed statistical relations with the SUV max and the PET score (p<0.008 and p=0.003 respectively). With respect to DFS, significant differences were detected for the PET stage and FLIPI risk (p=0.015 and p=0.047 respectively). FLIPI risk was the only significant predictor in Cox regression analysis, with a Hazard Ratio of 5.13 between high risk and low risk. CONCLUSION: The present research highlights the significant relation between metabolic variables obtained with FDG PET/CT and clinical variables although their goal as an independent factor of prognosis was not demonstrated in the present work.

[Quantitative and qualitative evaluation of the interim PET/CT in lymphoma treatment in the prediction of complete metabolic response]. / Evaluación cuantitativa y cualitativa de la PET/TC a mitad del tratamiento en linfomas en la predicción de respuesta metabólica completa.

OBJECTIVE: To compare two different methods for the interpretation of interim PET/CT (PET/CT-i) in lymphomas, and to establish which one best predicts a complete metabolic response (CMR) in the PET/CT study at the end of treatment (PET/CT-et). MATERIAL AND METHODS: Retrospective longitudinal analysis of the PET/CT studies for staging (PET/CT-s), PET/CT-i and PET/CT-et of 65 patients, 35 Hodgkin's lymphoma (HL) and 30 Non-HL. The PET/CT-i was performed between the second and fourth chemotherapy cycle. It was interpreted using two different criteria: qualitative criteria (5 point visual scale), semiquantitative criteria (percentage difference between the lesion with more SUVmax in the PET/CT-s and PET/CT-i). We analyzed the likelihood of obtaining a CMR in the PET/CT-et according to the results obtained on the PET/CT-i with these two criteria. RESULTS: We obtained sensitivity (S), specificity (Sp), positive predictive values (PPV), negative predictive values (NPV) and likelihood ratio (LR) for the qualitative/semiquantitative method of 91%/80%, 76.2%/67%, 88.9%/83.3%, 80%/60.9% and 32%/7.8%, respectively, to predict a CMR in the PET/CT-et. There were no statistically significant differences between the LR of both methods (p=0.1942). CONCLUSION: We found clear differences in S, Sp, PPV and NPV between both interpretation criteria for the PET/CT-i to predict a CMR in the PET/CT-et. Nevertheless, we cannot confirm the superiority of the qualitative method over the semiqualitative method for this purpose as no statistically significance differences were found in their LR in our study.

18F-FDG-PET/CT in the surveillance of patients with lymphoma: detection of asymptomatic recurrences.

AIM: To assess the diagnostic accuracy of (18)F-FDG-PET/CT in detecting asymptomatic recurrences in patients with lymphoma. To define uptake patterns of recurrence indicative of recurrence. MATERIAL AND METHODS: Those patients with lymphoma who fulfilled the following inclusion criteria of clinical complete remission and negative PET/CT study were included retrospectively and longitudinally. Conventional surveillance of these patients was performed only by (18)F-FDG PET/CT following a standardized procedure. Pathologic locations (supra- and infradiaphragmatic) and their character (single or multiple) were analyzed in order to determine reliable metabolic patterns of recurrence. The final diagnosis was established by histopathological analysis or clinical follow-up greater than 8 months. RESULTS: A total of 199 explorations belonging to 106 patients with lymphoma were included. Of these patients, 59 had Hodgkin's lymphoma and 47 non-Hodgkin's lymphoma. There was suspicion of relapse from the metabolic point of view in 27 of the PET/CT scans. Of these, 14 (10 patients) were false positive (FP), and 13 (8 patients) true positive. The remaining studies were true negative, no false negatives being detected. The pattern most frequently related to recurrence was infradiaphragmatic lymph node involvement while most of the FP had isolated supradiaphragmatic involvement. Sensitivity, specificity, PPV, NPV and diagnostic accuracy of PET/CT parameters for the study were 100%, 92%, 48%, 100% and 93%, respectively. CONCLUSION: (18)F-FDG-PET/CT is a sensitive technique in the detection of asymptomatic recurrences in patients with lymphoma during their follow-up. Multiple character and infradiaphragmatic locations were the patterns that best correlated to the diagnosis of recurrence.

[PET-CT with intravenous contrast in the evaluation of patients with lymphoma. Contribution to diagnostic indications]. / PET-TAC con contraste intravenoso en la valoración de pacientes con linfoma. Aproximación hacia las indicaciones diagnósticas.

AIM: To define the utility of intravenous contrast administration in the PET-CT (PET-CTc) in patients with lymphoma in order to determine its possible indications. MATERIAL AND METHODS: 78 patients with lymphoma were prospectively evaluated. All underwent simultaneous PET-CTc scans in a hybrid system for staging (8), evaluation of response to treatment (29), suspicion of recurrence (9) and complete remission control (48). The PET scan was acquired by a conventional method and the diagnostic CT scan was performed according to radiological protocol. Both examinations were evaluated blinded and independently, analyzing 28 anatomical locations in order to determine the degree of agreement. Final diagnosis was established by the clinician based on the histological study, results of other diagnostic techniques or clinical follow-up. RESULTS: The final result of both techniques were concordant in 87/94 studies (92.5%). A total of 158 (36 FP) pathological locations were detected with PET-CT and 189 (71 FP) with CTc, with 72 locations being discordant between both techniques. Global sensitivity, specificity, PPV and NPV were 93%, 98%, 77% and 99%; and 94%, 97%, 62% and 99%, respectively. CONCLUSIONS: Administration of intravenous contrast does not seem to provide any advantage in the determination of nodal and extranodal disease in lymphoma patients. The low prevalence of disease probably accounts for the limited PPV of both techniques. An increase of our sample size, with a greater homogeneity of the groups, should offer more reliable results.