Sequential Targeted Treatment for a Geriatric Patient with Acute Myeloid Leukemia with Concurrent FLT3-TKD and IDH1 Mutations

Nearly 20,000 patients are diagnosed with acute myeloid leukemia (AML) in the US annually.¹ Despite the use of aggressive chemotherapeutic agents, the prognosis remains poor, with a mean 5-year survival of 28.3%.² Fortunately, with the refinement of next-generation sequencing (NGS) hematology panels and development of systemic targeted therapies, the treatment landscape for eligible patients has improved, both in frontline and relapsed or refractory (R/R) patients.

Specifically, investigations into alterations within the FMS-like tyrosine kinase (FLT3) and isocitrate dehydrogenase (IDH) genes have led to the discovery of a number of targeted treatments. Midostaurin is US Food and Drug Administration (FDA)-approved for use in combination with induction chemotherapy for patients with internal tandem duplication of the FLT3 (FLT3-ITD) gene or mutations within the tyrosine kinase domain (FLT3-TKD).³ Ivosidenib is indicated for frontline treatment for those who are poor candidates for induction chemotherapy, and R/R patients who have an R132H mutation in IDH1.^4,5 Enasidenib is FDA-approved for R/R patients with R140Q, R172S, and R172K mutations in IDH2.⁶

The optimal treatment for patients with AML with ≥ 2 clinically actionable mutations has not been established. In this article we describe a geriatric patient who initially was diagnosed with AML with concurrent FLT3-TKD and IDH1 mutations and received targeted, sequential management. We detail changes in disease phenotype and mutational status by repeating an NGS hematology panel and cytogenetic studies after each stage of therapy. Lastly, we discuss the clonal evolution apparent within leukemic cells with use of ≥ 1 or more targeted agents.

Case Presentation

A 68-year-old man presented to the Emergency Department at The Durham Veterans Affairs Medical Center in North Carolina with fatigue and light-headedness. Because of his symptoms and pancytopenia, a bone marrow aspiration and trephine biopsy were performed, which showed 57% myeloblasts, 12% promyelocytes/myelocytes, and 2% metamyelocytes in 20 to 30% cellular bone marrow. Flow cytometry confirmed a blast population consistent with AML. A LeukoVantage (Quest Diagnostics) hematologic NGS panel revealed the presence of FLT3-TKD, IDH1, RUNX1, BCOR-E1477, and SF3B1 mutations (Table). Initial fluorescence in situ hybridization (FISH) results showed a normal pattern of hybridization with no translocations. His disease was deemed to be intermediate-high risk because of the presence of FLT3-TKD and RUNX1 mutations, despite the normal cytogenetic profile and absence of additional clinical features.

Induction chemotherapy was started with idarubicin, 12 mg/m², on days 1 to 3 and cytarabine, 200 mg/m², on days 1 to 7. Because of the presence of a FLT3-TKD mutation, midostaurin was planned for days 8 to 21. After induction chemotherapy, a bone marrow biopsy on day 14 revealed an acellular marrow with no observed myeloblasts. A bone marrow biopsy conducted before initiating consolidation therapy, revealed 30% cellularity with morphologic remission. However, flow cytometry found 5% myeloblasts expressing CD34, CD117, CD13, CD38, and HLA-DR, consistent with measurable residual disease. He received 2 cycles of consolidation therapy with high-dose cytarabine combined with midostaurin. After the patient's second cycle of consolidation, he continued to experience transfusion-dependent cytopenias. Another bone marrow evaluation demonstrated 10% cellularity with nearly all cells appearing to be myeloblasts. A repeat LeukoVantage NGS panel demonstrated undetectable FLT3-TKD mutation and persistent IDH1-R123C mutation. FISH studies revealed a complex karyotype with monosomy of chromosomes 5 and 7 and trisomy of chromosome 8.

We discussed with the patient and his family the options available, which included initiating targeted therapy for his IDH1 mutation, administering hypomethylation therapy with or without venetoclax, or pursuing palliative measures. We collectively decided to pursue therapy with single-agent oral ivosidenib, 500 mg daily. After 1 month of treatment, our patient developed worsening fatigue. His white blood cell count had increased to > 43 k/cm², raising concern for differentiation syndrome.

A review of the peripheral smear showed a wide-spectrum of maturing granulocytes, with a large percentage of blasts. Peripheral flow cytometry confirmed a blast population of 15%. After a short period of symptom improvement with steroids, the patient developed worsening confusion. Brain imaging identified 2 subdural hemorrhages. Because of a significant peripheral blast population and the development of these hemorrhages, palliative measures were pursued, and the patient was discharged to an inpatient hospice facility. A final NGS panel performed from peripheral blood detected mutations in IDH1, RUNX1, PTPN11, NRAS, BCOR-E1443, and SF3B1 genes.