FDG PET-CT in Primary Staging and Management of Hodgkin Lymphoma (HL) and Non-Hodgkin Lymphoma (NHL): Experience in 465 Consecutive Patients.
Authors: Fulham Michael J. , Gibson Melinda , Trotman Judith , Forsyth Cecily , Cunningham Ilona , Mohamed Armin , Young Graham 
Published: October 2019

Abstract
Despite the utilization of Positron Emission Tomography (PET) with 18-F-fluorodeoxyglucose (FDG) in the evaluation of the lymphomas there are limited data on the role of PET-CT in staging and management of previously untreated HL and NHL. In this study we analysed the impact of PET-CT in 465 consecutive patients (223 females, 242 males; mean age = 52 years) who were scanned between June 2003 and June 2006. All scans were carried out on an LSO Biograph Duo PET-CT scanner. FDG isotope dose and scanning parameters were identical for all patients and scans; contrast was not given. PET-CT scans were read without access to histology or other imaging. Histology was HL (n=105) and NHL (n=360). In HL nodular sclerosing comprised 50% and in NHL, diffuse large B cell lymphoma accounted for 44% and follicular lymphoma 30%. Referring doctors were asked to provide the clinical stage, results of other investigations and the management plan prior to the scan. After the PET-CT scan they were asked for a revised clinical stage and management plan based on the PET-CT. Pre- and post-staging and management plans were compared. The analysis was retrospective in 176 and prospective in 289 patients. There were 81 Referring Doctors; 83% were Hemato-Oncologists. The PET-CT scans showed no abnormalities in 45 patients (5 HL, 40 NHL): 40 where the only site of disease was resected, and 5 where lesions were beyond the scanner resolution (1 conjunctival MALT, 4 cutaneous NHL); all were included in the analysis. Pre- and post PET-CT staging data were obtained in all 465 patients. PET-CT altered staging in 168 (36%) patients (38 HL, 130 NHL). Up-staging was seen in 149 (36 HL, 113 NHL), down-staging in 19 (2 HL, 17 NHL). Overall aggressive lymphomas showed markedly increased FDG uptake and there was only mild to moderately increased FDG uptake in most indolent lymphomas. FDG uptake, using Standard Uptake Values (SUVs), was defined as marked if SUV was >8, moderate if the SUV was between 4–8, and mild if the SUV was <4. FDG uptake was not uniform across all the lesions identified in many patients and there was heterogeneous uptake. We defined heterogeneity as focal regions of abnormal FDG uptake, which varied from mild to moderate or marked within the same patient. Heterogeneous FDG uptake was seen in 51% of HL and 40% of NHL patients, which was independent of the size of the lesions. In NHL this heterogeneity was seen in 48% of patients with indolent histology. Pre and Post PET-CT management plans were obtained in 417 (89%); the 48 patients without a management plan were excluded from further analysis. Management was changed in 117 (28%) patients (20 HL, 97 NHL); this comprised 55/149 (37%) patients who were upstaged, 56/297 (19%) patients where staging was unchanged and 6/19 (32%) patients who were downstaged. Where staging was unchanged, the altered management related to delineation of limited or more extensive disease on PET-CT in 54%. These results indicate that heterogeneity, independent of lesion size is common, in indolent lymphomas and may reflect different biological behaviour. Further, in the largest PET-CT cohort yet reported, PET-CT improves primary staging in HL and NHL and referrers appear to alter management based on these data.