18F-FDG cerebellum/liver index as a prognostic factor for progression-free survival in diffuse large B-cell lymphoma.

Objective: 18F-FDG PET/CT provides valuable informations regarding the prognosis of DLBCL. The aim of this study is to test a novel index based on cerebellar uptake to predict progression free survival in DLBCL patients.

Methods: Data from patients with de novo DLBCL between January 2011 and December 2018 were retrospectively collected and PFS was determined. The conventional PET parameters (SUV and total metabolic tumor volume) and the CLIP, corresponding to the ratio of the cerebellum SUV over the liver SUV, were extracted from baseline 18F-FDG PET.

Results: Ninety-five patients were included. When using a threshold of 3.24, CLIP was a significant predictor of PFS on univariate analysis (HR 3.4, p < 0.001) with different 5-year survival rates: 68% (CLIP ≥ 3.24) versus 32% (CLIP < 3.24). Multivariate analysis confirmed the prognostic value of CLIP, as it is one of the two factors remaining significant with β2-microglobulin (HR 2.1 and 2.5 respectively, p = 0.04 and p = 0.03). A score associating β2-microglobulin and CLIP allowed to separate the population into three groups of different outcome in terms of 5-year PFS: low risk (80%), intermediate risk (42%) and high risk (17%).

Conclusions: The CLIP derived from pre-therapeutic 18F-FDG PET seems to be an interesting predictive marker of PFS in DLBCL treated by immunochemotherapy.