Abstract
In glioma patients, complete resection of the contrast-enhancing portion is associated with improved survival, which, however, cannot be achieved in a considerable number of patients. Here, we evaluated the prognostic value of O-(2-[18F]-fluoroethyl)-L-tyrosine (FET) PET in not completely resectable glioma patients with minimal or absent contrast enhancement before temozolomide chemoradiation. Dynamic FET PET scans were performed in 18 newly diagnosed patients with partially resected (n = 8) or biopsied (n = 10) IDH-wildtype astrocytic glioma before initiation of temozolomide chemoradiation. Static and dynamic FET PET parameters, as well as contrast-enhancing volumes on MRI, were calculated. Using receiver operating characteristic analyses, threshold values for which the product of paired values for sensitivity and specificity reached a maximum were obtained. Subsequently, the prognostic values of FET PET parameters and contrast-enhancing volumes on MRI were evaluated using univariate Kaplan–Meier and multivariate Cox regression (including the MTV, age, MGMT promoter methylation, and contrast-enhancing volume) survival analyses for progression-free and overall survival (PFS, OS). On MRI, eight patients had no contrast enhancement; the remaining patients had minimal contrast-enhancing volumes (range, 0.2–5.3 mL). Univariate analyses revealed that smaller pre-irradiation FET PET tumor volumes were significantly correlated with a more favorable PFS (7.9 vs. 4.2 months; threshold, 14.8 mL; P = 0.012) and OS (16.6 vs. 9.0 months; threshold, 23.8 mL; P = 0.002). In contrast, mean tumor-to-brain ratios and time-to-peak values were only associated with a longer PFS (P = 0.048 and P = 0.045, respectively). Furthermore, the pre-irradiation FET PET tumor volume remained significant in multivariate analyses (P = 0.043), indicating an independent predictor for OS. Our results suggest that pre-irradiation FET PET parameters have a prognostic impact in this subgroup of patients.
Highlights
Astrocytic gliomas represent a pheno- and genotypically defined group of central nervous system neoplasms characterized by a rapid and infiltrative g rowth[1]
The recent interim analysis of the CATNON trial suggests that in patients with isocitrate dehydrogenase (IDH)-wildtype astrocytic gliomas, radiotherapy combined with maintenance temozolomide chemotherapy is of limited e fficacy[2]
From 2013–2019, we retrospectively identified patients who (i) were diagnosed with newly diagnosed and histomolecularly characterized IDH-wildtype astrocytic glioma not eligible for complete resection, showed (ii) minimal (i.e., ≤ 5 mL) or absent MRI contrast enhancement, and (iii) had undergone MR and FET PET imaging before initiation of radiotherapy
Summary
Astrocytic gliomas represent a pheno- and genotypically defined group of central nervous system neoplasms characterized by a rapid and infiltrative g rowth[1]. Despite the availability of a standardized treatment comprising surgery followed by chemoradiation with alkylating agents, the patients’ prognosis remains poor This poor prognosis applies to astrocytic glioma patients without an isocitrate dehydrogenase (IDH) mutation and an only incompletely resectable tumor due to its localization in deep or eloquent brain areas. A considerable number of patients especially with IDH-wildtype anaplastic glioma lack contrast enhancement on MRI8,9, so this parameter cannot be used for resection guidance and assessment. In this patient group, the limited information about the extent of the tumor tissue to be resected may contribute to the poor survival prognosis. We retrospectively identified prognostically unfavorable patients with non-completely resectable, IDH-wildtype astrocytic glioma with minimal or absent contrast enhancement on MRI. To identify a subgroup with improved progression-free and overall survival (PFS, OS), we evaluated the prognostic value of static and dynamic FET PET parameters before initiation of chemoradiation with temozolomide
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