posterior_fossa_a_ependymoma

Posterior Fossa A ependymoma

Posterior fossa ependymoma comprise three distinct molecular variants, termed PF-EPN-A (PFA), PF-EPN-B (PFB), and PF-EPN-SE (subependymoma) 1).


While supratentorial ependymomas are characterized by recurrent oncogenic fusions, infratentorial ependymomas can be classified by their epigenetic signatures into two main groups, pediatric-type (PFA) and adult-type (PFB) ependymomas


Group A patients are younger, have laterally located tumors with a balanced genome, and are much more likely to exhibit recurrence, metastasis at recurrence, and death compared with Group B patients. Identification and optimization of immunohistochemical (IHC) markers for PF ependymoma subgroups allowed validation of findings on a third independent cohort, using a human ependymoma tissue microarray, and provides a tool for prospective prognostication and stratification of PF ependymoma patients 2).

H3K27me3 (me3) loss by immunohistochemistry (IHC) is a surrogate marker for PFA wherein its loss is attributed to overexpression of Cxorf67/EZH2 inhibitory protein (EZHIP), C17orf96, and ATRX loss. Nambirajan et al. aimed to subgroup posterior fossa ependymomas using me3 IHC and study correlations of the molecular subgroups with other histone-related proteins, 1q gain, Tenascin C, and outcome. IHC for me3, acetyl-H3K27, H3K27M, ATRX, EZH2, EZHIP, C17orf96, Tenascin C, and fluorescence in-situ hybridization for chromosome 1q25 locus were performed on an ambispective posterior fossa ependymomas cohort (2003-2019). H3K27M-mutant gliomas were included for comparison. Among 69 patients, PFA (me3 loss) constituted 64%. EZHIP overexpression and 1q gain were exclusive to PFA seen in 72% and 19%, respectively. Tenascin C was more frequently positive in PFA (p = 0.02). H3K27M expression and ATRX loss were noted in one case of PFA-EPN each. All H3K27M-mutant gliomas (n = 8) and PFA-EPN (n = 1) were EZHIP negative. C17orf96 and acetyl-H3K27 expression did not correlate with me3 loss. H3K27me3 is a robust surrogate for PF-EPN molecular subgrouping. EZHIP overexpression was exclusive to PFA EPNs and was characteristically absent in Diffuse midline glioma H3 K27M-mutants and the rare PFA harboring H3K27M mutations representing mutually exclusive pathways leading to me3 loss 3).

Ramaswamy and Taylor found that the strongest predictor of poor outcome in patients with posterior fossa ependymoma across the entire age spectrum was molecular subgroup PFA, which was reported in the paper entitled “Therapeutic impact of cytoreductive surgery and irradiation of posterior fossa ependymoma in the molecular era: a retrospective multicohort analysis” in the Journal of Clinical Oncology. Patients with incompletely resected PFA tumors had a very poor outcome despite receiving adjuvant radiation therapy, whereas a substantial proportion of patients with PFB tumors can be cured with surgery alone 4).


A total of 72 Posterior fossa ependymomas cases were identified, 89% of which were PFA. The 10-year progression-free survival rate for all patients with PFA was poor at 37.1% (95% confidence interval, 25.9%-53.1%). Analysis of consecutive 10-year epochs revealed significant improvements in progression-free survival and/or overall survival over time. This pertains to the increase in the rate of gross (macroscopic) total resection from 35% to 77% and the use of upfront radiotherapy increasing from 65% to 96% over the observed period and confirmed in a multivariable model. Using a mixed linear model, analysis of longitudinal neuropsychological outcomes restricted to patients with PFA who were treated with focal irradiation demonstrated significant continuous declines in the full-scale intelligence quotient over time with upfront conformal radiotherapy, even when correcting for hydrocephalus, number of surgeries, and age at diagnosis (-1.33 ± 0.42 points/year; P = .0042) 5).

Effective treatment is limited to surgical resection and focal radiotherapy.


1)
Cavalli FMG, Hübner JM, Sharma T, Luu B, Sill M, Zapotocky M, Mack SC, Witt H, Lin T, Shih DJH, Ho B, Santi M, Emery L, Hukin J, Dunham C, McLendon RE, Lipp ES, Gururangan S, Grossbach A, French P, Kros JM, van Veelen MC, Rao AAN, Giannini C, Leary S, Jung S, Faria CC, Mora J, Schüller U, Alonso MM, Chan JA, Klekner A, Chambless LB, Hwang EI, Massimino M, Eberhart CG, Karajannis MA, Lu B, Liau LM, Zollo M, Ferrucci V, Carlotti C, Tirapelli DPC, Tabori U, Bouffet E, Ryzhova M, Ellison DW, Merchant TE, Gilbert MR, Armstrong TS, Korshunov A, Pfister SM, Taylor MD, Aldape K, Pajtler KW, Kool M, Ramaswamy V. Heterogeneity within the PF-EPN-B ependymoma subgroup. Acta Neuropathol. 2018 Aug;136(2):227-237. doi: 10.1007/s00401-018-1888-x. Epub 2018 Jul 17. PMID: 30019219; PMCID: PMC6373486.
2)
Witt H, Mack SC, Ryzhova M, Bender S, Sill M, Isserlin R, Benner A, Hielscher T, Milde T, Remke M, Jones DT, Northcott PA, Garzia L, Bertrand KC, Wittmann A, Yao Y, Roberts SS, Massimi L, Van Meter T, Weiss WA, Gupta N, Grajkowska W, Lach B, Cho YJ, von Deimling A, Kulozik AE, Witt O, Bader GD, Hawkins CE, Tabori U, Guha A, Rutka JT, Lichter P, Korshunov A, Taylor MD, Pfister SM. Delineation of two clinically and molecularly distinct subgroups of posterior fossa ependymoma. Cancer Cell. 2011 Aug 16;20(2):143-57. doi: 10.1016/j.ccr.2011.07.007. PMID: 21840481; PMCID: PMC4154494.
3)
Nambirajan A, Sharma A, Rajeshwari M, Boorgula MT, Doddamani R, Garg A, Suri V, Sarkar C, Sharma MC. EZH2 inhibitory protein (EZHIP/Cxorf67) expression correlates strongly with H3K27me3 loss in posterior fossa ependymomas and is mutually exclusive with H3K27M mutations. Brain Tumor Pathol. 2020 Nov 1. doi: 10.1007/s10014-020-00385-9. Epub ahead of print. Erratum in: Brain Tumor Pathol. 2021 Jan 9;: PMID: 33130928.
4)
Ramaswamy V, Taylor MD. Treatment implications of posterior fossa ependymoma subgroups. Chin J Cancer. 2016 Nov 15;35(1):93. doi: 10.1186/s40880-016-0155-6. PMID: 27846874; PMCID: PMC5111181.
5)
Zapotocky M, Beera K, Adamski J, Laperierre N, Guger S, Janzen L, Lassaletta A, Figueiredo Nobre L, Bartels U, Tabori U, Hawkins C, Urbach S, Tsang DS, Dirks PB, Taylor MD, Bouffet E, Mabbott DJ, Ramaswamy V. Survival and functional outcomes of molecularly defined childhood posterior fossa ependymoma: Cure at a cost. Cancer. 2019 Jun 1;125(11):1867-1876. doi: 10.1002/cncr.31995. Epub 2019 Feb 15. PMID: 30768777; PMCID: PMC6508980.
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  • Last modified: 2021/01/10 14:04
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