Whole-body diffusion-weighted MRI and 18F-FDG PET/CT can discriminate between different lymphoma subtypes

- Indolent non-Hodgkin lymphoma (NHL) showed significantly lower mean apparent diffusion coefficient (ADC) values than the other two lymphoma groups.
- The overall analysis (OS) showed a relationship between increased mean ADC and longer OS.
- DWI could be a useful method for visualizing transformation from indolent to aggressive NHL.

AimTo determine whether combined 2-[18F]-fluoro-2-deoxy-d-glucose (18F-FDG) positron-emission tomography (PET)/computed tomography (CT) and diffusion-weighted imaging (DWI) can be used for characterisation of different lymphoma subtypes, i.e., indolent versus aggressive lymphoma, and also to assess the prognostic value of different quantitative parameters of whole-body (WB) DWI and 18F-FDG PET/CT.Materials and methodsPre-therapeutic WB magnetic resonance imaging (MRI) including DWI and 18F-FDG PET/CT were performed in lymphoma patients. Different quantitative DWI and 18F-FDG PET/CT parameters were evaluated for characterisation of different lymphoma subtypes. These parameters were also correlated, both separately and in combination, against overall survival (OS) and progression-free survival (PFS). A lesion-by-lesion analysis was performed for correlation analysis between maximum standardised uptake value (SUVmax), mean standardised uptake value (SUVmean) and mean apparent diffusion coefficient (ADC).ResultsFifty patients were included in the study and divided into three groups: Hodgkin's lymphoma (HL), n=12; aggressive non-Hodgkin's lymphoma (NHL), n=29 (including 20 patients with diffuse large B-cell lymphoma, DLBCL); and indolent NHL, n=9. Indolent NHL showed significantly lower mean ADC values than the other two lymphoma groups (p=0.013). Aggressive NHL had a higher SUVmax than HL. The OS analysis of all patients showed a relationship (p=0.006) between increased mean ADC and longer OS. A model with both SUVmean and mean ADC, strengthened the possibility to predict PFS; however, a separate analysis of the DLBCL patients showed that none of the quantitative parameters could predict OS or PFS.ConclusionADC can discriminate between indolent and aggressive NHL. This finding can be useful in assessing possible transformation from indolent to aggressive NHL. ADC, ADC/SUV, and SUV cannot predict OS/PFS independent of lymphoma subtype.