Page 129 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation
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PET improves DLBCL response predictors DLBCL; PET; Deauville score; ∆SUVmax; metabolic tumor volume
Introduction
Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of non- Hodgkin lymphoma, characterized by an aggressive clinical course. Standard first- line treatment consists of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) generally administered at 2-wk (R-CHOP14) or 3-wk (R-CHOP21) intervals.
No significant benefits were shown for R-CHOP14 versus R-CHOP21 in 2 large randomized clinical trials [1,2]. Approximately 25%-40% of DLBCL patients experience relapse or progression in the first years after diagnosis. This problem underlines the need for early stratification between good and poor responders [3,4]. An early switch to second-line treatment in poor responders might improve patient outcomes.
The international prognostic index (IPI) and age-adjusted IPI (aaIPI), both consisting of baseline clinical characteristics, have retained prognostic value after the introduction of rituximab [5]. However, these prognostic indices are not widely used for individual treatment adaptation except for research purposes [6], do not inform about chemosensitivity, and are unable to identify a subgroup with survival clearly below 50%. Therefore, a powerful biomarker (e.g. imaging characteristics during treatment reflecting chemosensitivity) of early response is needed. Recently, measurement of baseline metabolic tumor volume (MTV ) was reported to have prognostic value in DLBCL and was suggested as an alternative to IPI [7,8]. Combining MTV with early response assessment at 18F-FDG interim PET (I-PET) further improved prediction of progression-free survival (PFS) [7,8]. Several operationalizations of I-PET response criteria have been proposed, such as the visual 5-point Deauville score (DS, with various possible cutoffs) [9] and quantitative changes in 18F-FDG uptake between baseline and I-PET [10,11].
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