High-dose radiation associated with improved survival in IDH-wildtype low-grade glioma

Knockdown of ATRX enhances radiosensitivity in glioblastoma

BACKGROUND

Glioblastoma are highly malignant type of primary brain tumors. Treatment for glioblastoma multiforme (GBM) generally involves surgery combined with chemotherapy and radiotherapy. However, the development of tumoral chemo- and radioresistance induces complexities in clinical practice. Multiple signaling pathways are known to be involved in radiation-induced cell survival. However, the role of alpha-thalassemia X-linked mutant retardation syndrome (ATRX), a chromatin remodeling protein, in GBM radioresistance remains unclear.

METHODS

In the present study, the ATRX mutation rate in patients with glioma was obtained from The Cancer Genome Atlas, while its expression analyzed using bioinformatics. Datasets were also obtained from the Gene Expression Omnibus, and ATRX expression levels following irradiation of GBM were determined. The effects of ATRX on radiosensitivity were investigated using a knockdown assays.

RESULTS

The present study demonstrated that the ATRX mutation rate in patients with GBM was significantly lower than that in patients with low-grade glioma, and that patients harboring an ATRX mutation exhibited a prolonged survival, compared with to those harboring the wild-type gene. Single-cell RNA sequencing demonstrated that ATRX counts increased 2 days after irradiation, with ATRX expression levels also increasing in U-251MG radioresistant cells. Moreover, the results of in vitro irradiation assays revealed that ATRX expression was increased in U-251MG cells, while ATRX knockdown was associated with increased levels of radiosensitivity.

CONCLUSIONS

High ATRX expression levels in primary GBM may contribute to high levels of radioresistance. Thus ATRX is a potential target for overcoming the radioresistance in GBM.

Effectiveness and Safety of Different Postoperative Adjuvant Regimens in Patients with Low-Grade Gliomas: A Network Meta-Analysis

OBJECTIVE

This study aimed to investigate the effectiveness and safety of various adjuvant regimens in patients with low-grade gliomas and to further explore the optimal adjuvant treatment for patients with low-grade gliomas and the differences in the efficacy of each treatment regimens in different tumor types.

METHODS

A comprehensive search of the PubMed, Cochrane Library, Ovid, Embase, and Web of Science databases was conducted to screen randomized and nonrandomized controlled trials related to adjuvant therapy in patients with low-grade gliomas. The Cochrane quality assessment method and the Newcastle-Ottawa Scale were used to assess the quality of the included randomized and nonrandomized controlled trials, respectively. The data from previous studies were extracted using Excel and GetData Graph Digitizer 2.26 software, and network meta-analysis was performed using RevMan 5.3 and Stata 16.0 statistical software.

RESULTS

The specific ranking of 5-year progression-free survival (5-year PFS) for each treatment regimen from the best to the worst in patients with low-grade gliomas was surgery (S) combined with procarbazine, lomustine, and vincristine (S + PCV); surgery combined with standard radiotherapy and PCV multidrug chemotherapy (S + RT + PCV); surgery combined with standard radiotherapy and temozolomide monotherapy (S + RT + TMZ); surgery combined with enhanced radiotherapy (S + H-RT); surgery combined with standard radiotherapy (S + RT); surgery combined with TMZ (S + TMZ); and S. The 5-year overall survival (OS) ranking was S + RT + TMZ, S + RT + PCV, surgery combined with enhanced radiotherapy and TMZ monotherapy (S + H-RT + TMZ), S + H-RT, S + RT, and S. The 2-year progression-free survival ranking was S + RT + TMZ, S + PCV, S + RT, S + RT + PCV, S + TMZ, S + H-RT, and S. The 2-year overall survival ranking was S + RT + TMZ, S + H-RT + TMZ, S + RT, S + RT + PCV, S + H-RT, and S. The incidence of adverse events (≥3) was ranked from highest to lowest as follows: S + RT + PCV, S + RT + TMZ, S + PCV, S + H-RT, S + TMZ, and S + RT. In the isocitrate dehydrogenase 1/2 mutation nonchromosome 1p and 19q chromosome whole arm codeletion (IDHmt/noncoder) group, the S + RT + PCV and S + H-RT regimens had better 5-year PFS and 5-year OS. In the isocitrate dehydrogenase 1/2 mutation and chromosome 1p and 19q chromosome whole arm codeletion (IDHmt/coder) group, the 5-year PFS of each treatment regimen ranked from the best to the worst was S + RT + TMZ, S + RT + PCV, S + H-RT, S + RT, S + TMZ, and S. The order of 5-year OS from the best to the worst was S + H-RT, S + RT + TMZ, S + RT + PCV, S + RT, and S. In the isocitrate dehydrogenase 1/2 wild-type (IDHwt) group, the S + H-RT and S + TMZ regimens had better 5-year PFS.

CONCLUSIONS

This study revealed that both the S + RT + TMZ and S + RT + PCV regimens might be effective therapies for treating patients with low-grade gliomas. Among these, the S + RT + TMZ regimen seemed to be safer but might lead to tumor deterioration. In the IDHmt/coder type, the S + RT + TMZ scheme might have a significant advantage. In the IDHmt/noncoder type, the S + RT + PCV scheme might be more dominant, while in the IDHwt type, the S + H-RT and S + TMZ schemes also might be good treatment options.

Three-dimensional arterial spin labeling-guided dose painting radiotherapy for non-enhancing low-grade gliomas

PURPOSE

To investigate the feasibility and dosimetric characteristics of dose painting for non-enhancing low-grade gliomas (NE-LGGs) guided by three-dimensional arterial spin labeling (3D-ASL).

MATERIALS AND METHODS

Eighteen patients with NE-LGGs were enrolled. 3D-ASL, T2 fluid-attenuated inversion recovery (T2 Flair) and contrast-enhanced T1-weighted magnetic resonance images were obtained. The gross tumor volume (GTV) was delineated on the T2 Flair. The hyper-perfusion region of the GTV (GTV-ASL) was determined by 3D-ASL, and the GTV-SUB was obtained by subtracting the GTV-ASL from the GTV. The clinical target volume (CTV) was created by iso-tropically expanding the GTV by 1 cm. The planning target volume (PTV), PTV-ASL were obtained by expanding the external margins of the CTV, GTV-ASL, respectively. PTV-SUB was generated by subtracting PTV-ASL from PTV. Three plans were generated for each patient: a conventional plan (plan 1) without dose escalation delivering 95-110% of 45-60 Gy in 1.8-2 Gy fractions to the PTV and two dose-painting plans (plan 2 and plan 3) with dose escalating by 10-20% (range, 50-72 Gy) to the PTV-ASL based on plan 1. The plan 3 was obtained from plan 2 without the maximum dose constraint. The dosimetric differences among the three plans were compared.

RESULTS

The volume ratio of the PTV-ASL to the PTV was (23.49 ± 11.94)% (Z = - 3.724, P = 0.000). Compared with plan 1, D_2%, D_98% and D_mean of PTV-ASL increased by 14.67%,16.17% and 14.31% in plan2 and 19.84%,15.52% and 14.27% in plan3, respectively (P < 0.05); the D_2% of the PTV and PTV-SUB increased by 11.89% and 8.34% in plan 2, 15.89% and 8.49% in plan 3, respectively (P < 0.05). The PTV coverages were comparable among the three plans (P > 0.05). In plan 2 and plan 3, the conformity indexes decreased by 18.60% and 12.79%; while the homogeneity index increased by 1.43 and 2 times (P < 0.05). Compared with plan 1, the D_0.1 cc of brain stem and D_max of optic chiasma were slightly increased in plan 2 and plan 3, and the absolute doses met the dose constraint. The doses of the other organs at risk (OARs) were similar among the three plans (P > 0.05).

CONCLUSION

The dose delivered to hyper-perfusion volume derived from 3D-ASL can increased by 10-20% while respecting the constraints to the OARs for NE-LGGs, which provides a basis for future individualized and precise radiotherapy, especially if the contrast agent cannot be injected or when contrast enhancement is uncertain.

Emerging MR Imaging and Spectroscopic Methods to Study Brain Tumor Metabolism

Proton magnetic resonance spectroscopy (1H-MRS) provides a non-invasive biochemical profile of brain tumors. The conventional 1H-MRS methods present a few challenges mainly related to limited spatial coverage and low spatial and spectral resolutions. In the recent past, the advent and development of more sophisticated metabolic imaging and spectroscopic sequences have revolutionized the field of neuro-oncologic metabolomics. In this review article, we will briefly describe the scientific premises of three-dimensional echoplanar spectroscopic imaging (3D-EPSI), two-dimensional correlation spectroscopy (2D-COSY), and chemical exchange saturation technique (CEST) MRI techniques. Several published studies have shown how these emerging techniques can significantly impact the management of patients with glioma by determining histologic grades, molecular profiles, planning treatment strategies, and assessing the therapeutic responses. The purpose of this review article is to summarize the potential clinical applications of these techniques in studying brain tumor metabolism.