Thalamic high-grade gliomas in children: a distinct clinical subset?

Abstract

Pediatric high-grade gliomas (HGGs) of the thalamic region account for up to 13% of pediatric HGGs and usually result in only anecdotal long-term survival. Because very little is known about these tumors, we aimed to further characterize them. In our series of 99 pediatric thalamic HGGs, there were no significant differences in survival between patients with tumors affecting the thalamus alone (including bithalamic lesions) and patients with tumors affecting the thalamus plus adjacent structures. Tumor resection (event-free survival/overall survival) and an early treatment response to radiotherapy/chemotherapy (event-free survival) had independent prognostic significance, as shown by Kaplan-Meier and multivariate Cox regression analyses. When we compared clinical characteristics and outcomes of pediatric thalamic HGG with those of pediatric (nonthalamic) supratentorial (n = 177) as well as pediatric pontine HGG (including diffuse intrinsic pontine gliomas; n = 234), we found that thalamic HGG shared more similarities with pontine than with supratentorial HGG, but overall, it appeared to represent a clinically distinct subgroup of pediatric HGG. The varying extent of tumor resection in the different tumor localizations may play some role in the observed clinical differences, as shown by multivariate Cox regression analyses, but the tumor site itself was also identified as an independent prognostic parameter. Thus, an additional location-specific effect on survival and/or tumor biology, despite different neurosurgical accessibility, has to be considered. Therefore, future investigations should try to further characterize the obviously site-specific heterogeneity of pediatric HGG on a molecular genetic basis.

The H3.3 K27M mutation results in a poorer prognosis in brainstem gliomas than thalamic gliomas in adults

“…14 gliomas (15). Our data showed a genetic molecular correlation that was different between brainstem and thalamic gliomas in adults.…”

Pediatric Thalamic Gliomas: An Updated Review

“…Of these publications, 20 were case series (Table). 1,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] Histologically, the vast majority (70%-90%) of reported thalamic tumors are classified as astrocytoma. However, this literature is limited and difficult to interpret regarding histologic subtypes in children, as many studies combine age groups, are confined to more specific entities (eg, pilocytic astrocytoma (PA) or ''high-grade astrocytoma''), group biologically distinct entities (eg, PA and low-grade diffuse astrocytoma [DA] as ''low-grade astrocytoma''), or are single case reports.…”

“…12,15,25 However, it is likely that much of the perceived benefit of resection (and possibly grade) is conferred by the significant number of PAs included in most samples as well as the difficulty of distinguishing between PA and low-grade DA in small biopsies. Five-year survival rates for high-grade thalamic DA have tended to average 15% to 25% in the literature, 1,33 although these numbers are quite variable. Moreover, recent studies 13,21 have indicated that extent of resection may not be as prognostically important as originally believed, particularly in high-grade and/or bithalamic DA, which suggests that additional biologic factors related to thalamic location may be influencing outcome.…”

“…2017;141:1316-1323; doi: 10.5858/arpa.2017-0249-RA) N eoplasms originating in the thalamus are rare overall (1% of all brain tumors); however, they comprise approximately 5% of pediatric intracranial tumors and approach 15% of all malignant pediatric intracranial tumors in some series. 1 Prognosis, poor overall and difficult to assess in the uneven literature, is generally related to unilateral or bilateral presentations, histologic type, histologic grade, and resectability. Because of the essential functions of the thalamus and surrounding structures, as well as the difficult surgical approach to the midline, biopsy and resection were rare in the past.…”

“…But with improved surgical techniques, total or partial resection is now more frequently performed, particularly for noninfiltrating, low-grade tumors. [1][2][3][4][5][6][7][8][9][10][11][12][13] Additionally, children with even incompletely resected low-grade thalamic gliomas can have a 5-year overall survival rate greater than 80% with adjuvant chemotherapy and radiation. 13,14 Therefore, histologic verification is now thought to be critical for planning treatment, and, as a result, biopsy and total/subtotal resections are much more common today than in the past.…”