Detection of 2-Hydroxyglutarate by 3.0-Tesla Magnetic Resonance Spectroscopy in Gliomas with Rare IDH Mutations: Making Sense of “False-Positive” Cases

We have previously published a study on the reliable detection of 2-hydroxyglutarate (2HG) in lower-grade gliomas by magnetic resonance spectroscopy (MRS). In this short article, we re-evaluated five glioma cases originally assessed as isocitrate dehydrogenase (IDH) wildtype, which showed a high accumulation of 2HG, and were thought to be false-positives. A new primer was used for the detection of IDH2 mutation by Sanger sequencing. Adequate tissue for DNA analysis was available in 4 out of 5 cases. We found rare IDH2 mutations in two cases, with IDH2 R172W mutation in one case and IDH2 R172K mutation in another case. Both cases had very small mutant peaks, suggesting that the tumor volume was low in the tumor samples. Thus, the specificity of MRS for detecting IDH1/2 mutations was higher (81.3%) than that originally reported (72.2%). The detection of 2HG by MRS can aid in the diagnosis of rare, non-IDH1-R132H IDH1 and IDH2 mutations in gliomas.

Acute myeloid leukemia with IDH1 and IDH2 mutations: 2021 treatment algorithm

Acute myeloid leukemia is a genetically heterogeneous hematologic malignancy; approximately 20% of AML harbors a mutation in the isocitrate dehydrogenase (IDH) genes, IDH1 or IDH2. These recurrent mutations in key metabolic enzymes lead to the production of the oncometabolite 2-hydroxyglutarate, which promotes leukemogenesis through a block in normal myeloid differentiation. Since this discovery, selective oral inhibitors of mutant IDH1 and IDH2 have subsequently been developed and are now approved as single agent therapy, based on clinical efficacy observed within the original first-in-human trials. The investigation of IDH inhibitors in combination with standard therapies such as azacytidine, with intensive chemotherapy, and with other small molecule targeted therapies in rational combinations are currently under evaluation to further improve upon clinical efficacy.

Estimation of the occurrence rates of IDH1 and IDH2 mutations in gliomas and the reconsideration of IDH-wildtype anaplastic astrocytomas: an institutional experience

Objectives Most diffuse gliomas are reported to harbor isocitrate dehydrogenase ( IDH) mutations. However, when these mutations are tested in clinical practice, the results are often negative. Methods This study examined the frequency of IDH1 and IDH2 mutations in gliomas classified according to the revised 2016 World Health Organization classification, and investigated their prognostic relevance. We tested 87 gliomas for IDH1 and IDH2 mutations using the peptide nucleic acid clamp method. Results IDH1 mutations were observed in 42% of diffuse astrocytomas, 23% of anaplastic astrocytomas, all oligodendrogliomas and anaplastic oligodendrogliomas, and 17% of glioblastomas. An IDH2 mutation was identified in one case of diffuse astrocytoma. In the survival analysis of diffuse astrocytic tumors, patients with IDH1/2-wildtype anaplastic astrocytomas tended to have a poor prognosis, similar to that of glioblastomas. Conclusions IDH2 mutations were infrequent in gliomas. In anaplastic astrocytomas, the frequency of IDH1/2-wildtype was relatively high, and the prognosis of patients with this type of tumor was very similar to that of those with glioblastomas. It may therefore be necessary to reconsider the classification and treatment strategies for IDH1/2-wildtype anaplastic astrocytomas.

Oncogenetic landscape and clinical impact of IDH1 and IDH2 mutations in T-ALL

IDH1 and IDH2 mutations (IDH1/2Mut) are recognized as recurrent genetic alterations in acute myeloid leukemia (AML) and associated with both clinical impact and therapeutic opportunity due to the recent development of specific IDH1/2Mut inhibitors. In T-cell acute lymphoblastic leukemia (T-ALL), their incidence and prognostic implications remain poorly reported. Our targeted next-generation sequencing approach allowed comprehensive assessment of genotype across the entire IDH1 and IDH2 locus in 1085 consecutive unselected and newly diagnosed patients with T-ALL and identified 4% of, virtually exclusive (47 of 49 patients), IDH1/2Mut. Mutational patterns of IDH1/2Mut in T-ALL present some specific features compared to AML. Whereas IDH2R140Q mutation was frequent in T-ALL (25 of 51 mutations), the IDH2R172 AML hotspot was absent. IDH2 mutations were associated with older age, an immature phenotype, more frequent RAS gain-of-function mutations and epigenetic regulator loss-of-function alterations (DNMT3A and TET2). IDH2 mutations, contrary to IDH1 mutations, appeared to be an independent prognostic factor in multivariate analysis with the NOTCH1/FBXW7/RAS/PTEN classifier. IDH2Mut were significantly associated with a high cumulative incidence of relapse and very dismal outcome, suggesting that IDH2-mutated T-ALL cases should be identified at diagnosis in order to benefit from therapeutic intensification and/or specific IDH2 inhibitors.

NCOG-38. CLINICAL CHARACTERISTICS OF LOW GRADE GLIOMA PATIENTS WITH NON-CANONICAL IDH1 AND IDH2 MUTATIONS

BACKGROUND Low grade gliomas (LGGs) develop in young adults and represent 10-15% of all glial tumors. While LGG patients can have longer survival than higher grade tumors, progression, transformation, and ultimately mortality occurs. Mutations in Isocitrate dehydrogenase 1/2 (IDH1/IDH2) are prevalent in LGG and are responsible for gliomagenesis. The classic IDH1 mutation is located at 132 codon and represented as p.Arg132His, but there are non-canonical IDH1 and IDH2 mutations. We sought to compare clinical characteristics of LGG patients with classic IDH1 p.Arg132His mutation to LGG patients with non-canonical IDH1 and IDH2 mutations. METHODS We queried an IRB-approved registry retrospectively from 12/2004- 9/2019. We included IDH1/IDH2 mutant LGG (WHO grade II) and known IDH1 and IDH2 targeted mutation analysis using standard PCR followed by DNA sequencing to detect point mutations in IDH1/IDH2 genes. We obtained available clinical and histopathological data. We estimated progression-free survival (PFS), time to transformation (TT), and overall survival (OS) using Kaplan-Meier methods. RESULTS We identified 267 LGG patients with median follow-up of 9.1 yrs (95%CI 8.4-9.9 yrs). Classic IDH1 p.Arg132His mutation occurred in 223 (83.9%) patients. IDH2 mutations occurred in 14 (5.2%) patients. Non-canonical IDH1 mutations were in 30 (11.2%) patients and included the following mutations: p.Arg132Cys (13), p.Arg132Gly (10), p.Arg132Ser (4), p.Arg132Leu (1), p.Arg119Gln (1), and p.Arg172Met (1). Initial presentation, OS, and TT did not differ between IDH1/IDH2 groups. PFS differed significantly between groups with improved median PFS in IDH2 mutant LGG (5.4 yrs; 95%CI 3.5-25.2) versus classic IDH1 mutant LGG (4.1 yrs; 95%CI 3.7-4.9 yrs) and non-canonical IDH1 mutant LGG (2.6 yrs; 95%CI 2.1-4.8) (log-rank p=0.019). Notably, non-canonical mutations were more common in astrocytoma (22/30; 73.3%) than other LGG histologies (p=0.018). CONCLUSIONS In this cohort, LGG patients with non-canonical mutations have a shorter time to progression than patients with classic p.Arg132His mutation and IDH2 mutations.

P04.12 Characteristics of IDH-mutant gliomas with non-canonical IDH mutations

BACKGROUND About 10% of IDH-mutant gliomas harbor non-canonical IDH mutations (non-R132H IDH1 and IDH2 mutations). The aim of the present study was to analyze the characteristics of these gliomas in comparison to those of IDH1 R132H mutant gliomas. MATERIAL AND METHODS We retrospectively analyzed the characteristics of a multicentric series of 161 gliomas with non-canonical IDH mutations and compared them to those of consecutive series of 109 IDH1 R132H mutant gliomas. Medical, radiological and pathological were reviewed. RESULTS Median age at diagnosis was 35 years in gliomas with a non-canonical IDH1 mutation, 42 years in those with an IDH2 mutation and 44 years in those with an IDH1R132H mutation. A familial history of cancer was more frequent in gliomas with a non-canonical IDH mutation than in those with an IDH1 R132H mutation (22,3% vs 5,5%, p<0.05). In both IDH1 R132H-mutant and non-canonical IDH-mutant gliomas the most frequent location was the frontal lobe. Yet, compared to IDH1R132H-mutant gliomas those with a non-canonical IDH mutation had more frequently an infratentorial location (5,5% vs 0% p<0,05) and were more frequently multicentric (4,9%, versus 0.9%, p<0.05). Compared to IDH1R132H-mutant gliomas, gliomas with a non-canonical IDH1 mutation were more frequently astrocytomas (65.7% vs 45%, p<0.05) while those with an IDH2 mutation were more frequently oligodendrogliomas (82% vs 55%, p<0.05). The median overall survival in IDH1 R132H-mutant and non-canonical IDH-mutant gliomas was similar (122 versus 120 months). CONCLUSION Gliomas with non-canonical IDH mutations are associated with distinct clinical, radiological and histological characteristics. Their prognosis, however, is similar to that of gliomas with canonical IDH mutations.