Introduction: When to Seek Diagnostics for Refractory AML

Understanding when to seek diagnostic testing is crucial for people who have been treated for acute myeloid leukaemia. Refractory acute myeloid leukaemia refers to a situation where the disease has not responded to the first round of treatment, meaning that complete remission has not been achieved because the chemotherapy drugs did not kill enough leukaemia cells.^[1] On the other hand, relapsed AML describes circumstances where the leukaemia returns after a period of successful treatment and remission.^[4]

People who should undergo diagnostic evaluation include those who have completed their initial induction chemotherapy but continue to experience symptoms, or those who were previously in remission and begin noticing concerning changes. Between 10% and 40% of patients with AML do not respond to initial therapy and are categorized as having refractory disease.^[5] Meanwhile, most relapses occur within the first two years after finishing induction treatment, becoming less common as time passes, and after five years the chance of relapse becomes extremely small.^[4]

It is advisable to seek diagnostic testing when experiencing symptoms that mirror those present at the time of initial diagnosis, or when new symptoms emerge. These may include feeling exhausted for no clear reason, infections that persist or keep returning, feeling tired or breathless due to low red blood cell counts, unexpected bruising or bleeding such as nosebleeds or bleeding gums, joint or bone pain, or abdominal discomfort and bloating.^[19] Some people may notice the same symptoms they had before, while others may experience different or additional signs that something has changed in their body.^[11]

Diagnostic Methods for Refractory AML

The diagnostic process for determining whether AML is refractory or has relapsed closely mirrors the testing performed when the disease was first identified. The primary purpose of these tests is to confirm whether the leukaemia cells remain present despite treatment, whether they have returned after a period of absence, and to understand any changes in the characteristics of these cells that might influence treatment decisions.

Blood Tests

Blood tests form the foundation of diagnostic evaluation for refractory AML. These laboratory tests examine samples of your blood to look for abnormal numbers of white blood cells, red blood cells, and platelets. When AML is refractory or has relapsed, the balance of these blood cells becomes disrupted again, similar to what occurs at initial diagnosis. The presence of myeloblasts, which are immature white blood cells, in the bloodstream can indicate that the leukaemia has not been adequately controlled or has returned.^[2]

Blood tests are relatively straightforward procedures that involve drawing a sample from a vein, typically in your arm. The sample is then sent to a laboratory where specialists examine it under a microscope and use various techniques to count and characterize the different types of cells present. These tests provide rapid information about the current state of the disease and help doctors make timely decisions about next steps.

Bone Marrow Tests

Bone marrow examination represents the most definitive method for diagnosing refractory or relapsed AML. You will have bone marrow tests to confirm whether your AML has come back or has not responded to treatment.^[19] These tests are similar to those performed during initial diagnosis and involve obtaining samples directly from the bone marrow, which is where blood cells are produced and where leukaemia cells typically accumulate.

The bone marrow testing procedure involves two main components: aspiration and biopsy. During aspiration, a hollow needle is inserted into a bone, usually the hip bone, and a liquid sample of bone marrow is withdrawn. A biopsy involves taking a small, solid core of bone marrow tissue. These samples provide detailed information about the proportion of leukaemia cells present, their maturity level, and their characteristics. This information is essential for determining whether complete remission has been achieved or whether the disease remains active.

Genetic and Molecular Testing

One particularly important aspect of diagnostic testing for refractory AML involves looking for genetic changes in the leukaemia cells. Your medical team will send your blood and bone marrow samples to look for any new genetic changes in your leukaemia cells.^[19] These genetic analyses help your medical team work out the most suitable treatment for you, as different genetic mutations may respond to different targeted therapies.

For example, testing may identify mutations such as the FLT3 mutation, which can be treated with specific targeted drugs like gilteritinib. Similarly, the presence of certain protein markers like CD33 may make the disease responsive to particular treatments such as gemtuzumab ozogamicin.^[1] Understanding the genetic makeup of your leukaemia cells at the time of relapse or when the disease proves refractory is crucial because the genetic characteristics may have changed from what they were at initial diagnosis, potentially opening up new treatment possibilities or explaining why previous treatments did not work as expected.

Additional Diagnostic Procedures

In some situations, additional diagnostic procedures may be necessary to determine whether the leukaemia has spread beyond the blood and bone marrow. If there is concern that the leukaemia has affected the central nervous system, which includes the brain and spinal cord, doctors may perform a lumbar puncture. This procedure involves inserting a needle into the lower back to collect a sample of the fluid that surrounds the brain and spinal cord, which is then examined for the presence of leukaemia cells.^[1]

Imaging tests may also be used in certain circumstances, particularly if there is suspicion that leukaemia cells have formed solid tumours outside the bone marrow, a condition known as myeloid sarcoma. These tumours can develop in various parts of the body including the skin and gums.^[2] Imaging studies help doctors visualize these areas and plan appropriate treatment strategies.

Diagnostics for Clinical Trial Qualification

Clinical trials represent an important treatment option for people with refractory or relapsed AML, and specific diagnostic tests are required to determine eligibility for participation in these studies. Your medical team might suggest treatment as part of a clinical trial if there is one suitable for you, as this could allow you to access treatments that would not otherwise be available.^[19]

Standard Eligibility Criteria

Clinical trials typically require comprehensive diagnostic testing to establish that a patient meets the specific criteria for enrollment. The definition of refractory disease is not entirely consistent throughout medical literature, but the European LeukemiaNet generally defines it as the inability to attain complete remission or complete remission with incomplete haematologic recovery after two courses of intensive induction treatment.^[10] Diagnostic tests must document this lack of response to previous therapy through bone marrow examination showing persistent leukaemia cells.

For relapsed disease, diagnostic criteria usually specify the timing and nature of the relapse. Trials may distinguish between early relapse, which occurs within a certain timeframe after achieving remission, and late relapse, which happens after a longer disease-free period. The length of time the leukaemia was in remission is an important factor that medical teams consider when determining treatment options and clinical trial eligibility.^[1]

Molecular and Genetic Profiling for Trials

Many modern clinical trials for refractory or relapsed AML are designed to test targeted therapies that work against specific genetic mutations or molecular characteristics. Consequently, detailed genetic and molecular testing becomes a prerequisite for participation. Diagnostic evaluation must identify specific mutations such as FLT3, IDH2, or other genetic changes that the experimental therapy is designed to target.

For instance, trials testing drugs like enasidenib specifically require documentation of an IDH2 mutation through validated laboratory testing methods.^[7] The presence of such mutations must be confirmed through approved diagnostic tests before a patient can be considered for enrollment. This requirement ensures that the trial participants are those most likely to benefit from the specific therapy being studied.

Performance Status and Organ Function Testing

Beyond confirming the presence and characteristics of the leukaemia itself, clinical trial enrollment typically requires diagnostic tests that assess overall health status and organ function. These may include tests of kidney function, liver function, heart function through electrocardiograms, and general fitness assessments. Such testing helps ensure that participants can safely undergo the experimental treatment being studied.

Your age, overall health, and any other medical conditions you may have are important factors that influence both treatment decisions and clinical trial eligibility.^[19] Some people with relapsed or refractory AML may not be strong enough to have intensive chemotherapy, which affects both standard treatment options and the types of clinical trials for which they might qualify.^[1] Diagnostic testing helps medical teams determine which approach is most appropriate and safe for each individual.

Response Monitoring During Trials

Once enrolled in a clinical trial, participants undergo regular diagnostic monitoring to assess how they are responding to the experimental treatment. This typically involves repeated blood tests and bone marrow examinations at specified intervals. These monitoring procedures serve multiple purposes: they help determine whether the treatment is working, identify any side effects or complications early, and contribute to the overall scientific understanding of the therapy being tested.

The achievement of complete remission after receiving treatment has historically been considered essential for improving survival in patients with AML. Approximately 90% of patients who were alive three or five years after induction therapy had achieved complete remission after their initial treatment.^[3] Therefore, diagnostic tests that can accurately assess whether remission has been achieved are crucial both within clinical trials and in standard treatment settings.