We recently studied a pediatric patient with malignant transformation of ganglioglioma treated with bevacizumab and were able demonstrate the significant contribution of combined multimodal MRI and ¹⁸F-DOPA–PET in the early diagnosis of tumor “pseudoresponse” and non-enhancing tumor progression [29]. Anti-angiogenic agents, especially those targeting vascular endothelial growth factor, such as bevacizumab, are increasingly used in pediatric patients with high-grade tumors. Previous studies in adults demonstrated that the differentiation between brain tumor response and tumor progression following treatment with bevacizumab poses a complex diagnostic challenge. This monoclonal antibody produces a dramatic decrease in the contrast enhancement of the lesion on conventional MRI, a phenomenon called “pseudoresponse.” The prefix “pseudo” refers to the fact that the imaging change reflects restoration of the blood–brain barrier rather than a true tumor response. Despite this stably reduced or absent contrast enhancement, patients can develop neurological worsening, with an increase of T2/FLAIR MRI abnormalities on follow-up studies, in keeping with a pattern of non-enhancing but progressive disease. Since an objective criterion for non-enhancing tumor progression is currently unfeasible, these patients must be closely and repeatedly followed until a confident disease evaluation is possible, as this will significantly influence decision-making regarding treatment continuation or discontinuation.

Our results suggest that ¹⁸F-DOPA–PET imaging in patients treated with anti-angiogenesis agents deserves further investigation to evaluate the potentially promising role of this novel imaging modality [29]. Overall, on the basis of our preliminary experience in pediatric patients with brain tumors, the results obtained with¹⁸F-DOPA confirm previous data from adults [30] in terms of the impact of this tracer on patient management and/or treatment decisions. Further investigations with larger series are thus also needed to validate the use of amino acid PET tracers in improving diagnostic accuracy, monitoring dynamic changes within brain tumors during therapy, and establishing whether (and if so, how and when) these radiolabeled amino acids should become a critical part of the clinical management of pediatric patients with brain tumors. Correlation with MRI data is mandatory for an accurate interpretation of PET results and thus a close collaboration between neuroradiologists and nuclear medicine physicians. Greater efforts within the diagnostic imaging community should be directed at improving the integration of information obtained by different imaging modalities in order to overcome their respective limitations. The result will be a more robust tool in the crucial evaluation of pediatric brain tumors.