Metachronous oligodendroglial tumours with different IDH mutational profile in a young patient

Aims Oligodendroglioma is molecularly defined by mutation of isocitrate dehydrogenase (IDH) and 1p19q codeletion. IDH mutation is an early driver of tumorigenesis, via its oncometabolite 2-hydroxyglutarate, regardless of the exact mutational subtype in homologues IDH1 or IDH2. IDH mutant cells then acquire 1p19q codeletion, with haploinsufficiency likely to contribute to oncogenesis by reduced expression of genes on 1p and 19q, as well as mutations in TERT, FUBP1 (on 1p31.1) in ~30% and CIC (on 19q13.2) in ~>60% of 1p19q-codeleted gliomas. We present a case of a young patient with metachronous oligodendroglial tumours, initially thought to represent contralateral recurrence of the same disease. However, IDH mutation analysis in each tumour revealed distinct types of mutations, involving both IDH1 and IDH2, indicating different cellular lineages of tumorigenesis. We aim to present this unusual combination by illustrating the histology and molecular profile, and review the literature with regards to multifocal but molecularly distinct glioma. Method Case: The patient is a 33 year old man initially presenting with seizures, who was found to have a frontal lobe lesion (hence called tumour 1) with focal radiological enhancement, followed by a contralateral lesion in the parietal lobe 6 months later (hence designated as tumour 2). He underwent separate surgical debulking, and each time, tumour tissue was histologically and genetically examined. Testing included targeted mutation screening by immunohistochemistry and PCR based methods, pyrosequencing for MGMT methylation analysis, FISH for chromosomal LOH analysis of 1p and 19q, immunohistochemistry for mismatch repair enzymes and next generation sequencing. Results Histology of tumour 1 revealed a neoplasm with uniform cells, round nuclei and oligodendroglioma-like clear cell change, without mitoses, microvascular proliferation or necrosis. Immunohistochemistry showed absence of IDH1 R132H mutation, retained expression of ATRX and no altered p53 staining. The ki-67 index reached 6%. Sequencing of IDH1/2 mutations revealed a rare IDH2 mutation (non-/R172K). FISH confirmed codeletion of 1p19q, and the integrated diagnosis was oligodendroglioma, IDH mutant and 1p19q codeleted, WHO grade II. Histology of tumour 2 demonstrated oligodendroglioma morphology in areas, but more cellular and nuclear pleomorphism and focally brisk mitotic activity (7 mitoses in 10 hpf; ki67 index 20%), while both microvascular proliferation and necrosis were absent. Immunohistochemistry showed IDH1 R132H mutation and retained ATRX, while p53 was not expressed. FISH studies confirmed codeletion of 1p19q, and the integrated diagnosis was anaplastic oligodendroglioma, IDH mutant and 1p19q codeleted, WHO-2016 grade III. NGS data and MMR results are compared. Conclusion We present a patient with two histologically similar, but molecularly distinct oligodendroglial tumours affecting both cerebral hemispheres. Apart from the grade, the important difference is the presence of different IDH mutations, 1) a rare IDH2 mutation (non-R172K) and 2) the common IDH1 (R132H) mutation. While both types of IDH mutations identified are known to occur in oligodendroglioma, the difference clearly indicates two distinct lineages of tumorigenesis, especially as IDH mutation is considered an early event in gliomagenesis. IDH2 mutations are often associated with oligodendrogliomas, while IDH1 R132H is recognised to be frequent in both diffuse oligodendroglial and astroglial neoplasms. Multifocal divergent gliomas have been described previously but oligodendrogliomas with differing IDH mutations in the same patient have not knowingly been reported yet. Importantly, though therapeutically irrelevant here, multicentric gliomas do not automatically imply relatedness. However, a common origin or predisposition (here, even predating IDH mutation) may not be ruled out.

Identification of Isocitrate Dehydrogenase 2 (IDH2) Mutation in Carotid Body Paraganglioma

Carotid body paragangliomas (PGLs) are rare neuroendocrine tumors that develop within the adventitia of the medial aspect of the carotid bifurcation. Carotid body PGLs comprise about 65% of head and neck paragangliomas, however, their genetic background remains elusive. In the present study, we report one case of carotid body PGL with a somatic mutation in the gene encoding isocitrate dehydrogenase 2 (IDH2). The missense mutation in IDH2 resulted in R172G amino acid substitution, which exhibits neomorphic activity and production of D-2-hydroxyglutarate.

Biological Roles and Therapeutic Applications of IDH2 Mutations in Human Cancer

Isocitrate dehydrogenase (IDH) is a key metabolic enzyme catalyzing the interconversion of isocitrate to α-ketoglutarate (α-KG). Mutations in IDH lead to loss of normal enzymatic activity and gain of neomorphic activity that irreversibly converts α-KG to 2-hydroxyglutarate (2-HG), which can competitively inhibit a-KG-dependent enzymes, subsequently induces cell metabolic reprograming, inhibits cell differentiation, and initiates cell tumorigenesis. Encouragingly, this phenomenon can be reversed by specific small molecule inhibitors of IDH mutation. At present, small molecular inhibitors of IDH1 and IDH2 mutant have been developed, and promising progress has been made in preclinical and clinical development, showing encouraging results in patients with IDH2 mutant cancers. This review will focus on the biological roles of IDH2 mutation in tumorigenesis, and provide a proof-of-principle for the development and application of IDH2 mutant inhibitors for human cancer treatment.

Optimizing Response to Enasidenib with Dose Escalation: Case Series

Background: Isocitrate dehydrogenase enzymes catalyze the conversion of isocitrate to alpha-ketoglutarate. Mutated IDH enzymes generate the "oncometabolite" 2-hydroxyglutarate (2-HG), which inhibits TET2 function. IDH2 mutations have been reported in 9% to 19% of acute myeloid leukemia (AML) cases. Inhibition of the mutant IDH2 enzyme led to decreased 2-HG levels and induced myeloid differentiation in IDH2 mutant AML. Enasidenib, a small-molecule inhibitor of mutant IDH2, was approved in 2017, after a successful phase I/II trial showing an overall response rate (ORR) of 40.3% in relapsed/refractory (R/R) disease, with 19.3% of patients achieving complete remission (CR). A Phase III trial is currently ongoing. It targets the mutant IDH2 variants R140Q, R172S, and R172K; at an approved dose of 100 mg oral daily dose. At higher doses the drug was less tolerated, however, few subjects received dose modification at the 650 mg daily dose group; these events did not qualify as a dose-limiting toxicity (DLT). In this descriptive study, we are reporting a case series of R/R AML, with an IDH2 mutation, that are treated with escalated dose enasidenib. Method: This case series is based on retrospective observations of patients with R/R IDH2 mutant AML since January 2017, who are treated with enasidenib. We are reporting two cases treated with an escalated dose of 200 mg daily. We included patients with intermediate to poor-risk AML, who received at least one prior line of therapy, started on standard dose enasidenib (100 mg daily) for a minimum of 6 months and followed until disease relapse or death. We excluded patients who are primarily resistant to enasidenib (AML risk stratification and response evaluation by ELN-Leukemia NET. IDH2 mutations were identified by a local diagnostic laboratory that is regulated under CLIA through PCR which is validated to detect 10% or more mutant allele frequency. To quantify IDH2 variant frequency, confirmatory testing was performed via ARUP next-generation sequencing panel (NGS). Results: Here we report the descriptive outcomes of 2 cases from a single institution, who were treated with escalated dose enasidenib (200 mg oral daily) for R/R AML with an IDH2 mutation. The first case describes a 65-year-old female diagnosed with poor-risk AML in the setting of pancytopenia with bone marrow evaluation consistent with the background of erythroid and granulocytic dysplasia, with normal karyotype analysis. The patient has treated with induction chemotherapy and 2 cycles consolidation that was complicated with bacterial infections, prolonged hospitalization, and profound deconditioning led to stopping treatment. After 18 months of surveillance, repeat bone marrow evaluation for new-onset pancytopenia revealed relapsed AML with evidence of IDH2 mutation at codon 140, with a variant frequency of 36.9% by NGS. The case was started on enasidenib at 100 mg oral daily dose. After 6 months of therapy, the patient continued to be cytopenic, repeated bone marrow evaluation showed residual AML with IDH2 variant frequency of 27.6%. The decision was made to increase the enasidenib dose to 200 mg daily. With follow up for another 5 months on the escalated dose, the patient achieved hematologic complete response (hCR) with normalization of peripheral platelet count and ANC. [Figures 1-2] The patient maintained hCR for another 5 months on 200 mg enasidenib daily until she died from COVID-19 infection. The second case describes a 59-year-old female with poor-risk AML in the setting of leukocytosis, with bone marrow evaluation consistent with the background of megakaryocytic dysplasia and karyotype analysis positive for monosomy 7. The patient was treated with induction chemotherapy and failed to respond. Repeat bone marrow evaluation showed primary refractory disease with positive IDH2 mutation at codon 140 with a variant frequency of 40.7%. Treatment with 100 mg enasidenib was started. The patient maintained a partial response for 6 months, then peripheral blasts counts started to gradually increase. The decision was made to increase enasidenib dose to 200 mg daily, which improved peripheral blasts within one month of escalated dose therapy. [Figure 3] The patient maintained a response to therapy for another 3 months before she relapsed. Conclusion: Our limited data showed that initial response to standard dose enasidenib could potentially be optimized by dose escalation to 200 mg daily. Disclosures No relevant conflicts of interest to declare.

Mutations Based on Next-Generation Sequencing May be Complementally to Prognostic Risk in Myelodysplastic Syndromes

Objective: Established the value of somatic mutations based on next-generation sequencing (NGS) and explore factors associated with prognosis in myelodysplastic syndromes (MDS). Methods: From March 2012 to September 2019, 90 newly diagnosed MDS patients were treated and analysed by a sensitive NGS assay for mutations in 87 candidate genes and target regions. IPSSR higher risk include IPSS-R Intermediate, High, Very High subgroups (risk score >3.5), and IPSSR lower risk include IPSSR risk score ≤3.5. Results: A total of 90 MDS patients were recruited for this study (median age: 51.5 years; range: 16-70 years). Eighty-two (91.1%) patients harbored at least one mutation (median, 3 per patient; range, 0-11), and the most common mutations were found successively in the ASXL1 (28.9%), TP53 (21.1%), TET2 (18.9%), U2AF1 (17.8%), RUNX1 (15.6%), SETBP1 (13.3%), DNMT3A (13.3%), IDH1 (12.2%), NRAS (12.2%), KMT2D (11.1%), CBL (11.1%) and PTPN11 (11.1%) genes. The median follow-up was 32 months (range: 10-96 months). Thirty-seven (92.5%) had at least one point mutation in 40 patients with normal karyotype. ASXL1 and U2AF1 mutations had more frequently platelet levels of <50×109/L (P=0.047, P=0.023; respectively) and hemoglobin concentrations at <80 g/L (P=0.048, P=0.042; respectively). Compared with the lower risk MDS, more TP53 mutations (28% vs. 12.5%, P=0.048), RUNX1 mutations (22% vs. 7.5%, P=0.039), IDH1 mutations (18% vs. 5%, P=0.041), and IDH2 mutations (8% vs. 0, P=0.047) were found in the higher risk MDS. During the follow-up period, 37 (41.4%) patients translate to AML at a median follow-up of 24.5 months (range: 2-96 months). The median time of progress to AML from MDS diagnosis was 46 (2-96) months in MLD, 21 (2-37) months in EB1, and 18.5 (2-73) months in EB2. At 3-year follow-up, the probability of overall survival (OS) and cumulative incidence of AML transformation (CIAT) were 72.3% (95%CI 67.2%-77.8%) and 36.2% (95%CI 30.9%-41.5%), respectively. The univariate analysis results showed that ≥50 years old, IPSSR higher risk, ASXL1mutation, TP53 mutation, TET2 mutation, U2AF1 mutation, RUNX1 mutation, IDH1 mutation, IDH2 mutation, and ≥3 molecular mutations were poor factors for OS. The univariate analysis results associated with CIAT showed that IPSSR higher risk, TP53 mutation, RUNX1 mutation, IDH1 mutation, and IDH2 mutation were poor factors for CIAT.Multivariate adjust analysis showed that IPSSR higher risk, ASXL1 mutation, TP53 mutation, and RUNX1 mutation were independent prognosis factors associated with OS (HR=0.113, 95% CI: 0.093-0.199, P=0.003; HR=0.215, 95% CI: 0.103-0.623, P=0.025; HR=0.147, 95% CI: 0.084-0.506, P=0.012; HR=0.317, 95% CI: 0.122-0.661, P=0.013; respectively), and IPSSR higher risk, TP53 mutation, RUNX1 mutation, IDH1 mutation, and IDH2 mutation were independent prognosis factors associated with CIAT (HR=2.905, 95% CI: 1.155-6.312, P=0.023; HR=2.636, 95% CI: 1.024-5.023, P=0.004; HR=2.350, 95% CI: 1.043-5.789, P=0.024; HR=2.061, 95% CI: 1.036-4.078, P=0.003; HR=2.814, 95% CI: 1.073-5.359, P=0.005; respectively). Patients with mutations in one or more of the three independent survival prognostic genes (TP53, RUNX1, or ASXL1) defined as "mutation high risk" (n=48) and those without anyone of the three prognostic genes defined as "mutation low risk" (n=42). OS were significantly longer in the IPSSR both lower risk and higher risk patients with mutations low risk cohort than IPSSR lower risk patients with mutations high risk cohort (3-year OS, 95.7% vs. 47.1%, P=0.001; 79.9% vs. 47.1%, P=0.045; respectively). In the IPSSR lower risk with mutations high risk group, OS was significantly improved in the allo-HSCT cohort (3-year OS, 75.0% vs. 30.0%, P=0.042). In the IPSSR higher risk with mutations low risk group, no significant difference existed between the transplant and non-transplant arms for the probabilities of OS (3-year OS, 83.3% vs. 75.8%, P=0.972). Conclusions: Somatic mutations are common in MDS and are associated with prognosis. Mutation high risk may be complementally to IPSSR prognostic risk in MDS patients, and allo-HSCT can improved the survival in the IPSSR lower risk with mutations high risk group. Key words: myelodysplastic syndromes; somatic mutations; Prognostic dichotomization based on 3.5 of the revised international prognostic scoring system; overall survival; allogeneic stem cell transplantation. Disclosures No relevant conflicts of interest to declare.

Acquisition of IDH2 Mutations in Relapsed/Refractory AML Is Associated with Worse Patient Outcomes

Introduction Isocitrate dehydrogenase 2 (IDH2) is mutated in ~10% of acute myeloid leukemia (AML). However, the clonal evolution of IDH2 mutations through the course of AML has not been clearly elucidated. The presence of targeted therapy, Enasidenib, for the treatment of IDH2 mutated AML underscores the importance of understanding the clonal dynamics of IDH2 mutations. Methods IRB approval was obtained. In this study, we analyzed ~6000 patients with NGS results to identify 120 AML patients with IDH2 mutations and longitudinal next generation sequencing (NGS) testing. Disease status was determined for each NGS test date by chart review. IDH2 mutation status was chronicled for each of the following disease states: diagnosis, remission, relapse, and persistent disease. Cytogenetic risk category was based on ELN 2017 guidelines. Statistical analyses were performed using SPSS. Results Of the 120 patients, there were 62 patients (51.67%) with AML-NOS and 58 patients (48.33%) with AML with myelodysplasia-related changes (AML-MRC). The most commonly co-occurring mutated genes included DNMT3A, SRSF2, RUNX1, ASXL1, NRAS, BCOR, NPM1, STAG2, FLT3, and PHF6 in order of frequency. Concurrent IDH1 and IDH2 mutations were seen in 2 patients, although IDH1/2 mutations were previously reported to be mutually exclusive. Of the total patients with IDH2 mutations, 105 patients (88%) were IDH2-positive at the initial diagnosis and 15 patients (12%) were IDH2-negative at diagnosis and acquired the mutation later in disease. Of those 15 patients, 7 patients gained the mutation during persistent disease, 6 during relapse, and 2 at remission (neither of whom relapsed). Forty-eight patients (40%) who were IDH2-positive in a prior test were found to be IDH2-positive with persistent AML, while 11 patients (9%) with IDH2-positive AML lost the IDH2 mutation despite the presence of persistent AML. Twenty-one patients (18%) who were IDH2-positive in a prior test were found to remain IDH2-positive in remission, while 49 patients (41%) cleared the IDH2 mutation. Twenty-four patients (20%) with IDH2-positive AML were found to be IDH2-positive at disease relapse, while 7 patients (6%) lost the IDH2 mutation at relapse. Kaplan-Meier survival analysis and the log-rank test were used to analyze overall survival (OS) to control for confounding factors of AML category (AML-MRC vs AML-NOS) and cytogenetic risk (Figure 1). Patients who were IDH2-positive at diagnosis had significantly better survival than patients who gained the IDH2 mutation later in disease (Figure 1A, p=0.024). Patients who were IDH2-negative at remission had significantly improved survival compared to patients who were IDH2-positive at remission (Figure 1B, p=0.002). Patients who had lost the IDH2 mutation with persistent disease had significantly greater overall survival than those who remained IDH2-positive with persistent AML (Figure 1C, p=0.035). No significant difference in OS was found based on IDH2 mutation status at relapse. Conclusion In summary, in the largest study of IDH2 clonal dynamics to date, we found that IDH2 mutations are not stable during AML disease course and frequent genetic testing of AML patients in necessary to tailor personalized therapy. Most patients (70%) cleared IDH2 in disease remission. In those with refractory disease, 18% of IDH2+ AMLs lose IDH2. In the relapse setting, 22% of IDH2+ AML show loss of IDH2. Overall, 12% of patients gained IDH2 mutation later in disease course usually in the setting of refractory/relapsed AML. These patients, along with those who remained IDH2+ in remission and during refractory disease, fared worse than their counterparts. Thus, the longitudinal IDH2 mutation testing at different disease stages may be helpful in prognostic stratification. Figure 1 Disclosures Sallman: Agios, Bristol Myers Squibb, Celyad Oncology, Incyte, Intellia Therapeutics, Kite Pharma, Novartis, Syndax: Consultancy; Celgene, Jazz Pharma: Research Funding. Padron:BMS: Research Funding; Novartis: Honoraria; Kura: Research Funding; Incyte: Research Funding. Talati:Pfizer: Honoraria; BMS: Honoraria; Astellas: Speakers Bureau; Jazz: Speakers Bureau; AbbVie: Honoraria. Hussaini:Boston Biomedical: Consultancy; Stemline: Consultancy; Adaptive: Honoraria.

Thyroiditis: A Rare Manifestation of Enasidenib-Induced Differentiation Syndrome

Enasidenib is an FDA-approved isocitrate dehydrogenase 2 (IDH2) inhibitor, which is used in the treatment of acute myeloid leukemia (AML). We present a case of AML with an IDH2 mutation treated with a regimen of enasidenib and 5-azacitidine, where thyroiditis was noted to be a part of differentiation syndrome. The patient is a 77-year-old woman with IDH2-mutated AML who had initially been started on 100 mg of enasidenib and then presented with dyspnea and was diagnosed with pleural effusion – a common presentation with enasidenib – but was also noted to have thyroiditis. She was started on steroids, but due to continued hyperbilirubinemia and thyroiditis, her dose of enasidenib was reduced to half, which resulted in clinical improvement. This case demonstrates thyroiditis as one of the rare manifestations in the treatment of AML with enasidenib-induced differentiation syndrome.