Feasibility of cognitive sparing approaches in children with intracranial tumors requiring partial brain radiotherapy: A dosimetric study using tomotherapy

Abstract

AbstractBackground : To assess feasibility of sparing the neural stem cell compartment (NSC), hippocampus, andlimbic circuit during partial brain radiotherapy (PBRT) for pediatric intracranial tumors.Methods : Treatment plans were generated for the following pediatric intracranial tumors: low and highgrade gliomas, low grade brainstem glioma, optic nerve glioma, hypothalamic glioma, localized ependymoma,skull base sarcoma, central nervous system (CNS) germinoma (involved field radiotherapy [IFRT] andwhole ventricular radiotherapy [WVRT] ), and craniopharyngioma. For each pathology, standard intensitymodulatedradiotherapy (IMRT) plans were generated using helical tomotherapy, as well as IMRT planswhich spared limbic circuit, hippocampus, and NSC. Biologically equivalent dose for late effects (BEDlateeffects) was generated for limbic circuit, hippocampus, and NSC. Percent reduction in mean, maximum, andminimum physical dose and BED was calculated between plans.Results : We reduced mean physical dose and BEDlate effects to these critical structures by 44% and 47.9%respectively (range 5.4-78.8% and 7-80.3%). Greatest benefits in relative dose reduction were seen in highgrade hemispheric glioma cases; least relative dose reduction was seen in WVRT cases. Dosimetric coverageof treatment target (PTV) was equivalent in all cases as assessed by D95 and V100 metrics. Integral dose touninvolved brain was reduced by mean of 7.6% (range -19.3% to +0.3%) in sparing plans.Conclusions : It is possible to spare limbic circuit, NSC, and hippocampus during PBRT for primary pediatricintracranial tumors using helical tomotherapy. This approach reduces integral dose delivered to uninvolvednormal brain and may reduce late cognitive sequelae of cranial radiotherapy.