ISHL10 Abstract T016

Whole body functional and anatomical MRI: accuracy in staging and treatment response monitoring in childhood and adolescent Hodgkin’s Lymphoma compared to conventional multimodality imaging (CRUK C23580/A12707)

This is a single centre cohort trial to compare whole body MRI (WB-MRI) & conventional investigations for staging & treatment response monitoring in childhood Hodgkin’s lymphoma. A total of 50 patients (32 male, median age 16, range 6-19) prospectively underwent WB-MRI in addition to conventional CT and PET CT at initial staging and during response assessment (n=37) after 2 chemotherapy cycles. WB-MRI included axial/coronal FS T2/T1 TSE, axial FS DWI (5 b values 0 to 800), & dynamic contrast enhanced T1 FLASH through the liver/spleen. The reference standard disease status at 30 sites (17 nodal, 13 extra nodal) & Ann Arbour stage was assigned by a multidisciplinary committee using PET CT and CT, based on EURONET trial criteria (nodal positivity >2cm and/or focal 18-FDG uptake above background). Treatment response (progression, none, partial inadequate (PRi), partial adequate (PRa) and complete) was defined using nodal volume change & FDG avidity. WB-MRI was read in consensus by 2 radiologists blinded to conventional imaging. Based on pilot data, nodal positivity was defined as >2cm &/or mean ADC < 1.2 x10-3mm2 s-1. Nodes 1 to 2cm with ADC 1.2-1.8 were equivocal. Treatment response was assigned using nodal volume change and rise in ADC (cut off of 70% to differentiate between PRi & PRa). Agreement between WB-MRI and the reference was expressed as percentage concordance for all reported disease sites and kappa statistics. Equivocal sites were treated as disease positive. Results are uncorrected for discrepancies in nodal site description. A total of 44 (88%) patients were concordant for at least 80% of nodal sites, although only 12 (24%) achieved 100% concordance between WB-MRI and the reference standard. Equivalent results for extra nodal disease were 48 (96%) and 34 (68%) respectively. There was 72% agreement for stage (36/50), (kappa 0.56-moderate), with 10 (20%) patients under staged by WB-MRI and 4 (8%) over staged. There was 68% agreement for response classification (25/37) (kappa 0.34-fair) with response over estimated by WB-MRI in 4 (11%) & under estimated in 8 (22%). In conclusion, WB-MRI holds promise as an alternative to conventional staging modalities using ionising radiation, but levels of discordance suggest it is not ready to fully replace them. WB-MRI is attractive as a staging modality for paediatric lymphoma but disagreement with standard modalities suggests caution must be applied before introducing into staging algorithms.