Open-label, multicenter, uncontrolled and non-randomized study comparing 18F-FDG PET-Scan and diffusion MRI in the assessment of the early therapeutic response of Diffuse Large B-Cell Lymphoma.

High-grade lymphomas are characterized by noisy symptomatology and quick progression kinetics in the absence of treatment. The therapeutic strategy and prognosis of patients depend on the initial staging and evaluation of early therapeutic response. Positron emission tomography injected with labeled fluorodeoxyglucose (18F-FDG PET-CT) is recommended in the initial disease balance; It also has a prognostic value demonstrated in the evaluation of the intermediate and final response of treatment of malignant non-Hodgkin's lymphoma B (LMNH B) to large cells through a qualitative visual analysis using the 5-point scale of Deauville, but also thanks to a quantitative analysis with the measurement of the Delta SUV max. If the 18F-FDG PET-CT is referred to, it is not without constraint, it is notably an examination leading to exposure to ionizing radiation for the patient.

Diffusion MRI (DWI) is a non-irradiating technique based on the evaluation of the diffusion of water molecules allowing indirect qualitative and quantitative analysis of the tumor microstructure, cellularity and integrity of the cell membrane . The tumor is thus detected thanks to its hypercellularity and the mapping of the apparent diffusion coefficient (ADC).

Several recent studies have demonstrated the feasibility and interest of MRI scattering and measurement of CDA in tumor staging and early therapeutic evaluation of high grade lymphomas and more particularly diffuse large B-cell Lyphoma, The latter being characterized by a high nucleo-cytoplasmic cellularity and ratio which makes it possible to obtain a strong signal and low ADC values in diffusion MRI (5) (7) (8) (9) (10) (12) (13) (14). However, there are few studies comparing these two imaging techniques in the therapeutic evaluation of large cell LMNH B (6) (11) (15). The main limitations of the existing studies are their small size and, above all, the accuracy of the methodology for quantifying the measurement of therapeutic response and in particular in terms of quantitative analysis of CDA.

Inclusion Criteria:

• Patient with Diffuse Large B-Cell Lymphoma confirmed histologically
• Patient with a tumor mass defined as measurable according to the RECIST 1.1 criteria,
• Patient requiring a standard first-line chemotherapy treatment (Rituximab -Cyclophosphamide - Hydroxyadriamycin - Oncovin - Prednisone = R-CHOP every 21 days),
• Patient older than 18 years,
• Performance status less than or equal to 2,
• Biological assessment meeting the following criteria: creatinine <150 μmol / l or creatinine clearance> 40 ml / min, total bilirubin <30 μmol / l, transaminases <2.5 x ULN
• Patient of childbearing age must agree to use Means of effective contraception during the treatment period,
• Patient having read the information note and having signed informed consent,
• Patient with Health care insurance available.

Exclusion Criteria:

• History of malignant hemopathy or solid tumor
• History of previous chemotherapy
• Contraindication to one of the examinations studied (Claustrophobia, Pacemaker ...)
• Patient included in another clinical trial for which a period of exclusion is mentioned.
• Patient considered to be a vulnerable person; Vulnerable persons are defined in article L1121-5 to - 8: Pregnant women, women who are pregnant, women who are breastfeeding, Persons deprived of their liberty by a judicial or administrative decision, persons who are hospitalized without consent under Articles L. 3212-1 and L. 3213-1 which do not fall under the provisions of Article L. 1121-8 and persons admitted to a health or social institution for purposes other than research Persons who are the subject of a legal protection measure or are unable to give their consent.