PET imaging in the surgical management of pediatric brain tumors.

OBJECTIVE: The present article illustrates whether positron-emission tomography (PET) imaging may improve the surgical management of pediatric brain tumors (PBT) at different steps.
MATERIALS AND METHODS: Among 400 consecutive PBT treated between 1995 and 2005 at Erasme Hospital, Brussels, Belgium, we have studied with (18) F-2-fluoro-2-deoxy-D-glucose (FDG)-PET and/or L-(methyl-(11)C)methionine (MET)-PET and integrated PET images in the diagnostic workup of 126 selected cases. The selection criteria were mainly based on the lesion appearance on magnetic resonance (MR) sequences. Cases were selected when MR imaging showed limitations for (1) assessing the evolving nature of an incidental lesion (n = 54), (2) selecting targets for contributive and accurate biopsy (n = 32), and (3) delineating tumor tissue for maximal resection (n = 40). Whenever needed, PET images were integrated in the planning of image-guided surgical procedures (frame-based stereotactic biopsies (SB), frameless navigation-based resections, or leksell gamma knife radiosurgery).
RESULTS: Like in adults, PET imaging really helped the surgical management of the 126 children explored, which represented about 30% of all PBT, especially when the newly diagnosed brain lesion was (1) an incidental finding so that the choice between surgery and conservative MR follow-up was debated, and (2) so infiltrative or ill-defined on MR that the choice between biopsy and resection was hardly discussed. Integrating PET into the diagnostic workup of these two selected groups helped to (1) take a more appropriate decision in incidental lesions by detecting tumor/evolving tissue; (2) better understand complex cases by differentiating indolent and active components of the lesion; (3) improve target selection and diagnostic yield of stereotactic biopsies in gliomas; (4) illustrate the intratumoral histological heterogeneity in gliomas; (5) provide additional prognostic information; (6) reduce the number of trajectories in biopsies performed in eloquent areas such as the brainstem or the pineal region; (7) better delineate ill-defined PBT infiltrative along functional cortex than magnetic resonance imaging (MRI); (8) increase significantly, compared to using MRI alone, the number of total tumor resection and the amount of tumor tissue removed in PBT for which a total resection is a key-factor of survival; (9) target the resection on more active areas; (10) improve detection of tumor residues in the operative cavity at the early postoperative stage; (11) facilitate the decision of early second-look surgery for optimizing the radical resection; (12) improve the accuracy of the radiosurgical dosimetry planning.
CONCLUSIONS: PET imaging may improve the surgical management of PBT at the diagnostic, surgical, and post-operative steps. Integration of PET in the clinical workup of PBT inaugurates a new approach in which functional data can influence the therapeutic decision process. Although metabolic information from PET are valid and relevant for the clinical purposes, further studies are needed to assess whether PET-guidance may decrease surgical morbidity and increase children survival.