Dissecting the prognostic signature of patients with astrocytoma isocitrate dehydrogenase-mutant grade 4: a large multicenter, retrospective study

CDKN2A/B status versus morphology in diagnosing WHO grade 4 IDH-mutated astrocytomas: what is the clinical relevance?

PURPOSE

In the 2021 WHO classification system for central nervous system tumors, the diffuse glioma subgroup IDH-mutated (IDHm) astrocytomas WHO grade 4 was introduced. The diagnosis can be based upon molecular or histopathological morphological criteria. Here we explore whether phenotype and survival of IDHm astrocytomas WHO grade 4 differed across the criteria used for diagnosis.

METHODS

Patients with IDHm astrocytoma, WHO grade 4, were included from Sahlgrenska University Hospital and TCGA database. We created three subgroups based upon the criteria for diagnosis of WHO grade 4; (1) homozygous CDKN2A/B deletion; (2) morphological (necrosis and/or microvascular proliferation); (3) combined subgroup with both homozygous CDKN2A/B deletion and morphological grade 4 criteria.

RESULTS

We included 90 patients (local cohort, n = 35, TCGA cohort, n = 55) with IDHm astrocytoma, WHO grade 4. The median survival was 4.1 years (95% CI 3.0-5.3). Survival was comparable when the diagnosis was based on homozygous CDKN2A/B deletion and on morphological WHO grade 4 criteria (5.2 vs. 5.3 years). However, in the combined subgroup, survival was significantly shorter (2.8 years, p = 0.006).

CONCLUSION

The different subgroups of IDHm astrocytoma WHO grade 4 share similar characteristics. Patients whose tumors exhibit combined criteria have worse prognosis.

Catalytically distinct metabolic enzyme isocitrate dehydrogenase 1 mutants tune phenotype severity in tumor models

Mutations in isocitrate dehydrogenase 1 (IDH1) impart a neomorphic reaction that produces D-2-hydroxyglutarate (D2HG), which can inhibit DNA demethylases to drive tumorigenesis. Mutations affect residue R132 and display distinct catalytic profiles for D2HG production. We show that catalytic efficiency of D2HG production is greater in IDH1 R132Q than R132H mutants, and expression of IDH1 R132Q in cellular and xenograft models leads to higher D2HG concentrations in cells, tumors, and sera compared to R132H. Though expression of IDH1 R132Q leads to hypermethylation in DNA damage pathways, DNA hypomethylation is more notable when compared to IDH1 R132H expression. Transcriptome analysis shows increased expression of many pro-tumor pathways upon expression of IDH1 R132Q versus R132H, including transcripts of EGFR and PI3K signaling pathways. Thus, IDH1 mutants appear to modulate D2HG levels via altered catalysis and are associated with distinct epigenetic and transcriptomic consequences, with higher D2HG levels appearing to be associated with more aggressive tumors.

Patient with recurrent grade 4 astrocytoma responding favorably to intranasal delivery of NEO100, highly pure perillyl alcohol: illustrative case

BACKGROUND

Better treatments are needed for patients with grade 4 gliomas, especially in the setting of recurrence. The authors are developing NEO100, a clinical-grade version of the natural monoterpene perillyl alcohol, as a cancer therapeutic to be administered via intranasal (IN) delivery to patients with recurrent glioma.

OBSERVATIONS

A 40-year-old woman was diagnosed with an isocitrate dehydrogenase 1-mutant, CNS WHO grade 4 astrocytoma harboring an unmethylated MGMT promoter. She underwent surgery and standard chemoradiation treatment with temozolomide (TMZ), but after 6 cycles of adjuvant TMZ, the tumor recurred. The patient was started on daily IN NEO100 at 288 mg 4 times a day, administered using a nebulizer and nasal mask. Routine MRI revealed steady tumor regression over the course of 13 months of daily IN NEO100, to the point where the tumor became inconspicuous. There were no serious adverse events, and her quality of life improved and remained high.

LESSONS

The authors present a case in which IN cancer therapy with NEO100 was well tolerated and was associated with striking tumor regression, providing further evidence that this novel conceptual approach to cancer therapy might become useful for the improved treatment of recurrent glioma. https://thejns.org/doi/10.3171/CASE24683.

Future Directions in the Treatment of Low-Grade Gliomas

ABSTRACT

There is major interest in deintensifying therapy for isocitrate dehydrogenase-mutant low-grade gliomas, including with single-agent cytostatic isocitrate dehydrogenase inhibitors. These efforts need head-to-head comparisons with proven modalities, such as chemoradiotherapy. Ongoing clinical trials now group tumors by intrinsic molecular subtype, rather than classic clinical risk factors. Advances in imaging, surgery, and radiotherapy have improved outcomes in low-grade gliomas. Emerging biomarkers, targeted therapies, immunotherapy, radionuclides, and novel medical devices are a promising frontier for future treatment. Diverse representation in glioma research and clinical trials will help to ensure that advancements in care are realized by all groups.