Diagnostic Assessment of 18F-fluciclovine and 18F-FDG -PET/MRI of Primary Central Nervous System Lymphoma

Primary central nervous system lymphoma (PCNSL) is a rare subtype of extranodal non-Hodgkins Lymphoma (NHL) with rising incidence and variable response to treatment. MRI is considered the most useful imaging modality of PCNSL, but conventional MRI has its limitations, and contrast-enhanced MRI sometimes does not clearly differentiate PCNSL from other neoplasm or non-neoplastic diseases. Positron emission tomography (PET) could have a number of potential advantages in refining and improving the management of patients with PCNSL. Because of the rare incidence of PCNSL, the value of PET has however not been well defined in this subtype of lymphomas. There are a few studies that have investigated the role for FDG-PET and amino acid PET in the primary staging/diagnosis and response assessment in PCNSL patients, but the results are inconclusive. Further studies are therefore needed. Previous studies support an integration of both MRI and PET for the routine diagnostic workup and response assessment for PCNSL, and the newly available simultaneous PET/MRI scanners may have the potential to improve imaging baseline accuracy, response assessment and add prognostic value in PCNSL. The main aim of the study is to compare the sensitivity and specificity of a combined PET/MRI examination with the clinical routine MRI examination given to these patients today. It will be investigated whether PET (18F-FDG and 18F-fluciclovine) can provide additional prognostic value at baseline and in response assessment compared to MRI and established pre-treatment prognostic scores in PCNSL, and evaluate which PET/MRI parameters that are best suited as an imaging biomarker for progression-free survival.