Gliomas are characterized by intratumoral histological heterogeneity, coexisting foci of low and high grade. First, in low-grade gliomas, neoangiogenesis has not yet developed and cellularity is low, so alterations on perfusion MRI may not be present. Second, a non-negligible number of high-grade gliomas show none, patchy, or weak contrast enhancement on MRI, so they can be misdiagnosed as low-grade glioma, preventing their correct management. We present 4 cases of patients in which 18F-fluorocholine PET defined the anaplastic tumor component and therefore the tumor aggressiveness, solving the limitations of MRI.

ObjectiveThe aim of this study was to assess the prognostic performance of postoperative 18F-fluorocholine PET/CT in patients with high-grade glioma (HGG).MethodsPatients with HGG who underwent preoperative and postoperative 18F-fluorocholine PET/CT were prospectively enrolled in the study. Postoperative MRI was classified as complete versus incomplete resection. Postoperative 18F-fluorocholine PET/CT was classified as negative (complete) or positive for metabolic residual tumor (incomplete resection) using a 5-point score system. The correlation of positive locations on PET/CT with the sites of subsequent tumor recurrence was evaluated. The concordance of postoperative imaging techniques (Cohen κ) and their relation with progression-free survival and overall survival were assessed using Kaplan-Meier method and Cox regression analysis.ResultsFifty-one studies, belonging to 47 patients, were assessed. Four patients underwent 2 postoperative 18F-fluorocholine PET/CT scans as they needed a second tumor resection for recurrence. In the follow-up, 42 patients progressed, and 37 died. Concordance between postoperative PET/CT and MRI assessment was poor. Resection grade on MRI did not show any significant association with prognosis. In multivariate analysis, only age and postoperative PET/CT showed significant association with progression-free survival (hazard ratio [HR], 1.03 [1.01–1.06, P = 0.006] and 1.88 [0.96–3.71, P = 0.067], respectively) and overall survival (HR, 1.04 [1.01–1.07, P = 0.004] and 2.63 [1.22–5.68, P = 0.014], respectively). Postoperative positive 18F-fluorocholine PET/CT locations correlated with the sites of subsequent tumor recurrence in 81.82% of cases.ConclusionPostoperative 18F-fluorocholine PET/CT seems superior to postoperative MRI in the outcome prediction of patients with HGG, outperforming it in the identification of the most probable location of tumor recurrence.

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