Predicting the Clinical Behavior of Pilocytic Astrocytomas in Children: Utility of Magnetic Resonance Spectroscopy

Keywords: children, magnetic resonance spectroscopy, outcome, astrocytoma, brain tumor

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     Despite generally favorable prognosis for children with pilocytic astrocytomas, outcomes are not always predictable.
     This study aims to establish the predictive value of magnetic resonance spectroscopy (MRS) in the clinical course of juvenile pilocytic astrocytoma (JPA; WHO Grade I).
     38 patients underwent surgical resection of tumor; 9 patients required multiple resections. Median age at diagnosis was 5 years (range: 1 month - 16 years). 5 patients received pre-resection chemotherapy with 1 patient also receiving radiation therapy. 10 patients received post-resection chemotherapy. No other patients received radiation therapy. All patients except one (n=37) were followed for at least 6 months post-operatively.
     Medical records from 40 patients (22 females) with histologically diagnosed JPA (Supratentorial-11; Infratentorial-29) and pre-treatment MRS scans were retrospectively analyzed under an IRB-approved protocol. All spectra were acquired using single-voxel, short-echo point-resolved spectroscopy.
     Patients were categorized by outcome: (1) progressive or recurrent disease at most recent follow-up or deceased (n=5), and (2) stable residual tumor or no evidence of disease (n=35). MRS data were analyzed for absolute concentration and concentration relative to creatine (Cr) concentration. The following six metabolites were found to be significantly higher in patients with progressive disease compared to those with non-progressive disease: (glutamine+glutamate)/Cr, lactate/Cr, N-acetyl-aspartate/Cr, and choline/Cr (p < 0.01); and citrate/Cr and LipMM13 (p < 0.05).
     This is a retrospective study.
     Progressive JPAs may have a distinct metabolic profile when compared with stable residual tumor.
     This discernible property may allow better prognostication of JPAs and aid in planning postoperative management.


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