Positron emission tomography (PET) with 18-fluoro-deoxy-glucose (PET-FDG) is emerging as a promising approach for detecting brain lesions in dementia, among which Alzheimer's disease has been the most widely studied.

Alteration of neuro-cognitive function induced by chemotherapy has been extensively documented in breast carcinoma patients. These modifications consist in the decrease of memory, intellectual capacity, speed analysis, and represent a real limitation for patients, sometimes durable. Aggressive lymphomas (diffuse large B cell lymphomas/DLBCL) represent a common disease, the standard being Rituximab-Cyclophosphamide-Doxorubicine-Vincristine-Prednisone (RCHOP) regiment which contains, as for breast cancer patients, anthracyclines. However, very little is known about the incidence and severity of cognitive function alteration in these patients. The occurrence of such complications should also be facilitated because of frail cognitive states due to age and co-morbidity. Cognitive function alteration is usually measured by neuropsychological tests (NPT) which are easy to handle and sensitive, but could lack specificity, in the context of general degradation which is often observed in hematological patients.

Positron emission tomography with 18-fluoro-deoxy-glucose (PET-FDG) is emerging as a promising approach for detecting brain lesions in dementia, among which Alzheimer's disease has been the most widely studied. In our center, the investigators have already described glucidic hypometabolism in several brain territories associated with Alzheimer's disease and other dementia. Moreover, uptake quantification and topography are useful markers for determining the type of the disease and progression. PET-FDG received very little attention for the detection of chemotherapy-induced brain damages.

Inclusion Criteria:

• histologically documented DLBCL
• previously untreated
• with International Prognostic Index (IPI) 0 or 1, or 2 without general state alteration (OMS≤2)
• submitted to RCHOP regimen (according to GELA's standard protocol)
• normal pre-treatment brain CT scan
• able to give informed consent
• speaking well French language
• benefiting from general medical insurance
• registered in the national listing of patients for biomedical research.

Exclusion Criteria:

• IPI > or =3
• medical history of another cancer, or psychiatric or pre-dementia disorder, or convulsion
• barbituric regular use which can't be stop
• human immunodeficiency virus (HIV) patients
• unstable diabetes mellitus
• pregnancy