18F-FDG PET in the Diagnosis and Treatment of Primary Central Nervous System Lymphoma

Abstract

This paper summarizes the usefulness and limitation of positron emission tomography (PET) with18F-fluorodeoxyglucose (18F-FDG) in the diagnosis and treatment of primary central nervous system lymphoma (PCNSL). The18F-FDG uptake in typical PCNSL is about 2.5 times higher than that in the normal gray matter, and the tumor can usually be identified visually. The18F-FDG uptake pattern and value provide useful information for differentiating PCNSL from other enhancing malignant brain tumors especially glioblastoma (GB). The18F-FDG uptake in typical PCNSL is usually homogenous, and the uptake value is significantly higher than that in GB. However,18F-FDG PET often fails to show the presence of tumor in the brain as18F-FDG uptake is faint in atypical PCNSL such as disseminated or nonenhancing lesions.18F-FDG PET is also useful for evaluating the treatment response at a very early stage after the initial treatment. Pretreatment and posttreatment18F-FDG uptake values may have a prognostic value in patients with PCNSL. In conclusion,18F-FDG PET is very useful in the diagnosis of typical PCNSL and can differentiate PCNSL from other malignant brain tumors. However, the usefulness of18F-FDG PET is limited in the diagnosis of atypical PCNSL.