Postoperative Metabolic Abnormality in Craniopharyngioma Patients Before Proton Therapy

Abstract

Purpose/Objective(s): To assess postoperative changes of cerebral glucose metabolism in craniopharyngioma patients receiving proton therapy. Materials/Methods: From 2011 to 2012, 17 patients enrolled in a prospective proton therapy trial for craniopharyngioma and received longitudinal PET and MR imaging for tumor and normal tissue response. Sixteen of them underwent craniotomies before baseline FDG PET studies followed by proton therapy of 54 CGEs. One did not require surgical intervention before radiation. Patient FDG PET images were nonlinearly warped to a 3D reference template in Talairach coordinates created from images of normal subjects. Left-right asymmetry of the count per voxel in each of 63 anatomical regions and region-based statistics of activity were computed. Regional asymmetry was considered significant when its Z score exceeded two standard deviations of normal population. To exclude any potential bias in PET acquisition, 12 control children with extracranial diseases but normal cerebral PET scans were also analyzed. Results: Median age of craniopharyngioma patients at diagnosis was 13 years (range, 4-18 years). Median time from craniotomies to baseline PET studies and from PET to proton therapy was 136 days (range, 7-226 days) and 32 days (range, 20-52 days). Significantly decreased glucose uptake was most prominent in right frontal lobe, striatum, and thalamus. It occurred in 7 of 10 patients who underwent transcranial craniotomies and in 2 of 3 patients receiving endoscopic craniostomy for cyst drainage, but in none of the 4 patients who received transphenoidal surgery or no surgery. Significant asymmetry in superior frontal gyrus is related to the surgical approach (89% occurrence in right frontal, bifrontal, and interhemispheric approaches vs 0% in other approaches). Significant asymmetry in caudate nucleus, putamen, and thalamus likely resulted from mass effect, venous occlusion, and surgical damage. A large, but not significant, uptake asymmetry (averaged 9%) in the inferior occipital gyrus was observed in both craniopharyngioma and control patients. This asymmetry is possibly due to the left occipital petalia commonly seen in right handers. None of the uptake asymmetry in superior frontal lobe, striatum, and thalamus was significant in control subjects. Conclusions: Postoperative metabolic abnormalities in the right superior frontal gyrus, striatum, and thalamus were noted in craniopharyngioma patients before proton therapy. The latter two are of particular interest since they subsequently receive the tumoricidal dose or are in high dose gradient regions and play an important role in regulation of motor control, sensory function, memory, sleep, and consciousness. The association with observed clinical deficits before and after proton therapy in this population will be reported. Author Disclosure: C. Hua: None. H.M. Conklin: None. M.A. Madey: None. D.J. Indelicato: None. B.L. Shulkin: None. T.E. Merchant: None.