Acute Myeloid Leukemia Treatment Options

Introduction

Leukaemia is a group of blood cancers caused by the uncontrolled proliferation of developing white blood cells called leukocytes.¹ The speed of proliferation classifies leukaemia as acute (fast-growing) or chronic (slow-growing), and the cell of origin determines if it is myelocytic or lymphocytic.¹

Acute myeloid leukaemia (AML) is the most common type of leukaemia in adults, accounting for over 80% of all cases.² AML begins in the bone marrow (the inner part of certain bones where new blood cells are made), but it rapidly goes into the bloodstream as well.^1,2

Treatment options in AML are critical for disease control, increased survival rates, personalised methods, relapse prevention, improved quality of life, and advancing research. These advances have resulted in higher overall survival rates, particularly among younger patients. Cure rates have grown to 15% in patients over 60, and over 40% in patients under 60, thanks to recent breakthroughs.²  Treatment methods also aim to reduce adverse effects and improve AML patients' quality of life.  

Diagnosis and staging

Diagnostic procedures for AML 

AML diagnosis procedures include a variety of tests and examinations designed to diagnose and characterise the disease:

• A thorough medical history review and physical examination revealed bruises, pallor, or hepatosplenomegaly (liver and spleen enlargement).²
• A complete blood count (CBC) determines the levels of red blood cells, white blood cells, and platelets. An abnormal CBC can suggest the presence of AML. 
• Bone marrow aspiration and biopsy involve extracting a small sample of bone marrow from the hip bone with a specific needle.² Then, the acquired sample is inspected under a microscope to look for leukaemia cells.
• Flow cytometry, cytogenetic analysis, immunophenotyping, and molecular testing may be used to provide more precise information about an AML subtype, identify particular genetic mutations, and guide treatment recommendations.²

Staging and risk assessment

Stages are commonly used to characterise the extent or spread of cancer. However, in AML instead of staging, for planning further management, its subtype and whether the disease has spread outside the blood and bone marrow are used.

AML can be categorised into different stages: untreated, remission, refractory, or recurrent. 

• In newly diagnosed (untreated) AML, the disease is in its initial stage and has not yet received any treatment. Key indicators of untreated AML include abnormal CBC, the presence of at least 20% blasts (leukaemia cells) in the bone marrow, and the manifestation of leukaemia-related signs or symptoms.² 
• AML in remission refers to a state where the disease has been treated, leading to normal complete blood count, less than 5% blasts in the bone marrow, and the absence of leukaemia symptoms in the brain, spinal cord, or other parts of the body. 
• Refractory AML means that cancer does not respond to initial chemotherapy and does not go into remission. 
• Recurrent AML indicates the reappearance of cancer after remission, potentially affecting the blood or bone marrow.

Standard treatment approaches

AML standard treatment includes a combination of induction, consolidation, and maintenance therapies. 

Induction therapy

Induction chemotherapy attempts to induce remission by destroying leukaemia cells and restoring normal blood cell production. In AML patients, induction therapy is the initial step towards long-term remission, laying the groundwork for later consolidation and maintenance therapies.

Chemotherapy regimens used in induction: Induction therapy often consists of a combination of chemotherapy suited to the patient's unique characteristics and disease subtype. These powerful drugs function by specifically targeting and eliminating leukaemia cells while causing minimal harm to healthy cells. Since 1970, anthracycline (e.g., daunorubicin or idarubicin) and cytarabine regimen, known as "7 + 3" induction therapy, has been the standard of care for AML. The standard dose and schedule consist of either daunorubicin or idarubicin given in conjunction with seven days of continuous cytarabine infusion.³

Supportive care during induction: To handle any adverse effects and consequences associated with this rigorous treatment approach, close monitoring, and supportive care are essential. Red blood cell and platelet transfusions are examples of supportive care provided. Antibiotics and antifungals are also used to treat infections.

Consolidation therapy

Consolidation therapy follows induction and consists of additional cycles of chemotherapy to eliminate any remaining leukaemia cells and lower the chance of relapse. 

High-dose chemotherapy and stem cell transplantation: Chemotherapy and hematopoietic stem cell transplantation (transplantation of immature cells that can develop into all types of blood cells) are two primary strategies for consolidation. Depending on the kind of leukaemia, the patient's fitness, and the availability of a stem cell donor, each strategy could be employed alone or in combination.³

Other consolidation approaches: Other consolidation therapy options include targeted therapies, immunotherapy, and involvement in clinical trials.  The precise consolidation regimen used is determined by unique patient conditions, disease features, and previous treatment responses.³

Maintenance therapy

Purpose of maintenance therapy: After consolidation and achievement of complete remission, maintenance therapy may be recommended to help prevent the recurrence of leukaemia.⁴

Drugs used in maintenance therapy: Researchers have investigated maintenance treatment options for AML. However, there is currently insufficient evidence to support any of these approaches as the established standard of care for maintenance therapy in AML. More research is needed to determine the effectiveness and safety of these treatments in preventing AML relapse and improving long-term outcomes.^4,5

Targeted therapies

Overview of targeted therapies in AML

Targeted therapy is a type of cancer treatment in which medications or other substances are used to find and destroy specific cancer cells. Targeted therapy comes in various forms.

Molecularly targeted drugs

FLT3 inhibitors: Midostaurin is used in combination with specific forms of chemotherapy to treat newly diagnosed individuals with AML with FLT3 gene mutation. Gilteritinib may be used to treat patients with refractory or recurrent AML with FLT3 gene mutation.

IDH inhibitors: Enasidenib is used to treat AML patients with a mutation in the IDH2 gene and ivosidenib for individuals with a mutation in the IDH1 gene.

Other targeted agents: Leukemia cells are killed, prevented from proliferating, or aided in maturing into white blood cells by arsenic trioxide and all-trans retinoic acid (ATRA). These medications are used to treat acute promyelocytic leukaemia, a form of AML.

Immunotherapies

Antibody-based therapies: Monoclonal antibodies are immune system proteins created in a lab to treat a wide range of illnesses. They can bind to a particular target on cancer cells, leading them to be eliminated, their growth stopped, or their ability to spread prevented.

CAR T-cell therapy: Short for chimeric antigen receptor T-cell therapy is an innovative immunotherapy approach. It involves modifying a patient's T cells, a type of immune cell, to recognise and attack cancer cells more effectively.

Stem cell transplantation

Allogeneic stem cell transplantation

In allogeneic stem cell transplantation, stem cells are obtained from a compatible donor, often a sibling or unrelated donor. 

Selection of suitable donors: Selecting a suitable donor involves matching human leukocyte antigens (HLA), proteins on the cells' surface, to minimise graft rejection risk.

Pre-transplant conditioning regimens: High-dose chemotherapy and/or radiation are administered to eliminate the patient's diseased cells and suppress the immune system. 

Autologous stem cell transplantation

In this case, the patient's stem cells are used for transplantation.

• Procedure and considerations: The patient's stem cells are taken and stored before the transplant. In this instance, the patient's stem cells are reintroduced to reconstruct the bone marrow and restore blood cell production. Conditioning regimens are still used to kill cancer cells.

Clinical trials and emerging therapies

The importance of clinical trials in AML

Clinical trials play a crucial role in advancing the treatment, assessing the efficacy and safety of innovative treatments, and investigating brand-new drug combinations. Participation in clinical trials provides eligible patients with access to innovative treatments that may not be available through standard care.

Promising experimental treatments

Several promising experimental treatments are being explored in the field of AML.

• Novel drugs and combinations: Combinations of different drugs, such as hypomethylating agents combined with targeted therapies or immunotherapies, are being evaluated to improve treatment outcomes.
• Gene and cellular therapies: Researchers are investigating targeted therapies that specifically inhibit genetic mutations or abnormalities found in AML cells. Examples include inhibitors targeting FLT3, IDH1, and IDH2 mutations. 

Supportive care and symptom management

Management of side effects from treatment

Closely monitoring patients for potential complications and taking appropriate measures to alleviate symptoms are important. For example, patients may experience myelosuppression, which leads to low blood cell counts. Supportive care measures, such as administration of growth factors or blood transfusions, can help manage these effects and reduce the risk of complications.

Infection prevention and management

Strict infection control measures, including hand hygiene, environmental cleanliness, and prophylactic antibiotics, are implemented to minimise the risk of infections. 

Palliative care and symptom control

Palliative care aims to relieve symptoms, improve the patient's comfort, and enhance their overall well-being. It focuses on managing pain, addressing psychological and emotional needs, and supporting the patient and their loved ones through their journey. 

Relapsed or refractory AML

Treatment options for relapse

In such situations, alternative treatment options are explored to achieve disease control and improve outcomes.

Salvage chemotherapy

One common approach is salvage chemotherapy. Salvage chemotherapy involves administering different combinations of chemotherapy drugs, often more intensive than the initial induction therapy, to eradicate the leukaemia cells.

Investigational approaches for refractory AML

For refractory AML cases, where the disease does not respond to initial induction therapy or salvage chemotherapy, investigational approaches are explored. These may include participation in clinical trials evaluating novel drugs, targeted therapies, immunotherapies, or combination regimens.⁶

Prognosis and follow-up

Prognostic factors in AML

Prognostic factors, such as cytogenetics, molecular markers, age, and performance status, help predict the outlook for AML patients.

Follow-up care and monitoring

Regular appointments enable monitoring of treatment response, detection of potential relapse, and management of treatment-related side effects. Follow-up care involves physical examinations, blood tests, and bone marrow evaluations.  Psychosocial support and survivorship care are also essential.

Summary

Acute Myeloid Leukemia treatment options depend on several factors, including the patient's age, overall health, and genetic characteristics of the leukaemia cells. The mainstay of AML treatment is induction chemotherapy, which aims to achieve remission, followed by consolidation therapy - further treatment to prevent relapse. Stem cell transplantation, either allogeneic or autologous, may be considered for eligible patients. Targeted therapies are emerging as promising options for specific genetic mutations. Clinical trials offer access to novel treatments and investigational approaches.