18F-DOPA Positron Emission Tomography in Medulloblastoma: 2 Case Reports

Background Medulloblastoma (MDB) is an aggressive embryonal brain tumor, with underlying altered genetics and biological pathways that account for very heterogeneous natural histories and clinical behaviors. Positron emission tomography (PET) using radiolabeled amino acids provides important metabolic information for the diagnosis of cerebral glioma but only a few data are available on amino acid PET in MDB. In particular, no cases of MDB imaging with 6-[18F]-fluoro-L-3,4-dihydroxyphenylalanine (F-DOPA) have previously been described. Case Description Two patients with different histologic subtypes of MDB were referred for F-DOPA PET to define the extent and metabolic degree of their diseases. The patients had a newly diagnosed large-cell/anaplastic MDB and a fourth relapse of classic MDB, respectively. F-DOPA PET was unremarkable in the first case; F-DOPA uptake was low in the second patient with the tumor/background ratio as high as 1.29. Comparison was made with magnetic resonance imaging, which showed fluid-attenuated inversion recovery positive diseases. Aggressive tumor growth was shown in the clinical course of both patients. Conclusions The 2 cases reported here suggest that sensitivity of F-DOPA PET in MDB can be low. However, more comprehensive data are needed to conclude on the overall accuracy of F-DOPA PET in MDB.