World CML Day 2026: Understanding Chronic Myeloid Leukaemia, Targeted Therapy and Molecular Monitoring

Chronic Myeloid Leukaemia (CML) is a slow-growing blood cancer that often causes no early symptoms and is often diagnosed in routine blood tests. When symptoms do occur, they may be easy to overlook or mistaken for other conditions. This makes awareness and timely medical evaluation important.

At the same time, understanding CML today goes beyond recognising its symptoms. Targeted therapies have transformed CML treatment over the past 25 years, while regular molecular monitoring now plays a central role in showing whether the disease is responding as expected. Reflecting this shift in care, World CML Day 2026, observed on 22 September, focuses on the theme “From Access to Monitoring: 25 Years Forward for Every CML Patient.” It highlights the need for patients to have access not only to effective treatment, but also to the testing and follow-up required to manage CML over the long term.

World CML Day 2026: Why 22 September Matters

World CML Day is observed every year on 22 September, and the date has a special connection to the disease itself. The numbers 9/22 represent chromosomes 9 and 22, which exchange genetic material in CML. This change creates the BCR::ABL1 fusion gene on the Philadelphia chromosome, a defining feature of the disease in most patients.

What began as an awareness initiative led by the patient community has grown into a global day that brings together people living with CML, families, healthcare professionals and advocacy groups. The aim is not only to improve understanding of CML, but also to draw attention to the care patients need throughout what is often a long-term treatment journey.

World CML Day 2026 Theme: “From Access to Monitoring: 25 Years Forward for Every CML Patient”

The 2026 theme marks 25 years since targeted therapy changed the course of CML treatment. Yet having effective medicine is only one part of good CML care. Patients also need timely diagnosis, consistent access to treatment and regular molecular monitoring so their doctors can see how well the disease is responding and adjust care when necessary.

The campaign therefore focuses on an important next step in CML care: making sure that the progress achieved over the past 25 years reaches every patient, including access to the monitoring and follow-up needed to benefit fully from treatment.

What is Chronic Myeloid Leukaemia (CML)?

Chronic myeloid leukaemia (CML) is a slowly progressing cancer of the blood and bone marrow in which the bone marrow produces too many white blood cells. It develops from myeloid blood-forming cells, which normally give rise to red blood cells, platelets and certain types of white blood cells. In CML, this normal process becomes disrupted and abnormal white blood cells begin to build up in the blood and bone marrow.

What makes CML particularly distinctive is the genetic change that drives the disease.

The Philadelphia Chromosome and BCR::ABL1

In most people with CML, pieces of chromosomes 9 and 22 exchange genetic material. This creates an altered chromosome 22 known as the Philadelphia chromosome and forms a new gene called BCR::ABL1.

The BCR::ABL1 gene produces an abnormal protein called a tyrosine kinase that remains continuously active. This sends signals that encourage blood-forming cells to grow and divide when they should not, leading to the excessive production of white blood cells seen in CML.

Importantly, the Philadelphia chromosome associated with CML is an acquired genetic change. It develops in blood-forming cells during a person’s lifetime and is not normally passed from parent to child.

Understanding this genetic change has been central to modern CML care. Because doctors know the specific abnormal protein driving the disease, treatments can be designed to target it directly. The same BCR::ABL1 abnormality can also be measured during treatment, making it possible to track how well the disease is responding over time.

Common Signs and Symptoms of CML

CML does not always cause noticeable symptoms, especially in its earlier stages. Some people first learn that something may be wrong when a routine blood test shows an unusually high white blood cell count. When symptoms do occur, they may develop gradually and can overlap with many other health conditions.

Possible signs and symptoms include:

• Persistent tiredness or weakness
• Unexplained weight loss
• Drenching night sweats
• Fever without a clear cause
• Pain, pressure or a feeling of fullness below the ribs on the left side, which may occur when the spleen is enlarged

These symptoms do not necessarily mean someone has CML. Fatigue, fever and weight loss can occur for many reasons. What matters is when symptoms persist, remain unexplained or occur alongside abnormal blood test results.

If CML is suspected, the next step is not to rely on symptoms alone, but to investigate the blood and look for the characteristic genetic changes associated with the disease. This is where diagnostic testing becomes important.

How is CML Diagnosed?

CML may first be suspected when a routine blood test shows an unusually high white blood cell count. Doctors then use a combination of blood tests and genetic testing to confirm whether CML is present and to identify the characteristic BCR::ABL1 abnormality.

Blood Tests

A complete blood count (CBC) with differential measures the number and types of blood cells. In CML, the white blood cell count is often raised, and other blood cell counts may also be affected. Doctors also review the person’s symptoms, medical history and physical findings, including whether the spleen is enlarged.

Tests for the Philadelphia Chromosome and BCR::ABL1

Confirming CML requires evidence of the genetic change that drives the disease. Tests may include:

• Cytogenetic analysis: Examines chromosomes to look for the Philadelphia chromosome.
• FISH (fluorescence in situ hybridisation): Uses fluorescent probes to detect the BCR::ABL1 rearrangement in blood or bone marrow cells.
• RT-PCR: A highly sensitive test that detects and measures BCR::ABL1. It is useful not only for diagnosis, but also for monitoring the disease during treatment.

A bone marrow examination may also be recommended in selected situations to provide further information about the disease and blood-forming cells. It is not necessarily required in every routine presentation of CML.

Once the diagnosis is confirmed, the focus shifts to treatment. Because CML is driven by the BCR::ABL1 tyrosine kinase, modern treatment is designed to target this abnormal signal directly.

How Targeted Therapy Changed CML Treatment

CML treatment changed significantly with the development of tyrosine kinase inhibitors (TKIs). These medicines are designed to block the abnormal tyrosine kinase activity produced by the BCR::ABL1 fusion gene, which drives the growth of CML cells. By targeting this specific abnormal signal, TKIs help control the excessive production of white blood cells.

For many patients, especially those diagnosed in the chronic phase, TKIs are the mainstay of treatment. Several medicines are now available, and the choice depends on factors such as the individual’s disease characteristics, overall health, other medical conditions, previous treatment and the side-effect profile of the drug.

Treatment also needs to remain flexible. If a person does not respond as expected, develops significant side effects or shows signs of resistance, the care team may adjust the dose, switch to another TKI or consider other treatment options. Stem cell transplantation, chemotherapy and other therapies still have a role in selected situations, particularly when CML is more advanced or does not respond adequately to targeted treatment.

The major shift in CML care is therefore not simply that better medicines are available. It is that treatment can now be guided by the specific biology of the disease. The next step is equally important: checking regularly whether that targeted treatment is continuing to work, which is where molecular monitoring becomes central.

Why Molecular Monitoring is Essential in CML Care

Starting treatment is only one part of managing CML. Doctors also need to know whether the treatment is reducing the amount of disease over time. This is where molecular monitoring becomes especially important.

Molecular monitoring uses highly sensitive blood tests to measure the level of BCR::ABL1, the genetic abnormality that drives CML. Rather than relying only on symptoms or routine blood counts, these tests show how much BCR::ABL1 remains in the blood and whether that level is falling as expected with treatment.

What Do BCR::ABL1 Results Tell Doctors?

Repeated molecular tests help the care team understand:

• whether the CML is responding adequately to treatment
• whether the response is being maintained over time
• whether BCR::ABL1 levels are falling at the expected pace
• whether closer assessment or a change in treatment may be needed

Doctors interpret each result alongside previous results rather than making decisions based on a single test alone. Current European LeukemiaNet recommendations use treatment-response milestones at different points during therapy to help assess whether the response remains favourable or whether further evaluation is needed.

How Often Is Molecular Monitoring Needed?

The frequency depends on how well the disease is responding and where the patient is in their treatment journey. Current recommendations advise BCR::ABL1 testing at least every three months until a major molecular response has been achieved and confirmed. Once the response is stable, testing may generally be spaced further apart, although more frequent monitoring may be needed if results begin to fluctuate or rise.

Importantly, feeling well does not mean monitoring is no longer necessary. CML may remain clinically quiet while molecular tests continue to provide information that symptoms alone cannot. Regular monitoring therefore gives both patients and doctors a clearer picture of how well treatment is controlling the disease and helps guide the next steps in care.

What if CML is Not Responding as Expected?

Not every person with CML responds to treatment in the same way, and an unexpected molecular test result does not automatically mean that treatment has failed. Doctors usually look at the pattern of BCR::ABL1 results over time, alongside blood counts, symptoms, treatment adherence and any side effects or other medicines that may be affecting therapy. Current recommendations advise against changing treatment based on a single molecular result alone.

If BCR::ABL1 levels are not falling as expected, remain higher than the recommended treatment milestones or begin to rise after an earlier response, the care team may:

• repeat molecular testing to confirm the trend
• review whether the medicine is being taken regularly and at the prescribed dose
• check for drug interactions or treatment-related problems
• test for BCR::ABL1 mutations that may make the current TKI less effective
• consider switching to another TKI when clinically appropriate

The choice of the next treatment depends on why the response is inadequate, which medicines have already been used, the presence of any resistance mutations, other health conditions and the patient’s overall treatment goals.

Most people with CML are diagnosed while the disease is still in the chronic phase. If CML progresses to more advanced disease or remains resistant despite several targeted therapies, treatment becomes more complex. In selected patients, allogeneic stem cell transplantation may then be considered.

An unexpected result does not necessarily mean that treatment has failed, but it does call for closer evaluation. Regular monitoring helps doctors identify changes early, understand what may be affecting the response and adjust the treatment plan when needed.

Living With CML Means Staying Engaged With Long-Term Care

For many people, CML becomes a condition that needs to be managed over years rather than only through a short course of treatment. That can bring its own challenges, from remembering daily medication to dealing with side effects and keeping up with regular tests. The goal is not only to control the disease, but also to help patients maintain their health and quality of life over the long period.

A few practical habits can make long-term CML care easier to manage:

• Take treatment exactly as prescribed. Missing doses can affect how well a TKI works, so any difficulty with taking the medicine regularly should be discussed with the care team rather than managed alone.
• Keep up with scheduled blood and molecular tests. These results show whether the response remains stable and help doctors identify changes that may need attention.
• Report side effects early. Persistent or troublesome symptoms should be discussed with the treating team. In some cases, treatment can be adjusted without compromising disease control.
• Share information about other medicines and health conditions. Drug interactions and co-existing conditions can influence which TKI is safest and most suitable.
• Keep track of your results. Knowing whether BCR::ABL1 levels are falling, stable or changing can make follow-up discussions easier to understand.

Current CML guidance also places increasing emphasis on quality of life, because many patients remain on TKI therapy for several years. Treatment decisions therefore need to balance disease control with side effects, other health conditions and the person’s individual priorities.

Questions Worth Asking Your Doctor

Patients may find it helpful to ask:

• What does my latest BCR::ABL1 result mean?
• Is my CML responding as expected?
• How often will I need molecular testing?
• Which side effects should I report?
• What would make you consider changing my treatment?

These conversations are important because long-term CML care works best when patients understand not only what treatment they are taking, but also how their response is being measured and what the next step may be.

Expert CML Care at RGCIRC

At Rajiv Gandhi Cancer Institute & Research Centre (RGCIRC), CML care is supported by a dedicated haemato-oncology team that works closely with haematopathology and molecular diagnostics specialists. This is especially important in CML, where treatment decisions depend not only on blood counts and clinical findings, but also on identifying and monitoring the BCR::ABL1 abnormality over time.

RGCIRC’s molecular laboratory provides BCR-ABL1 testing and other advanced haematology investigations, while the haemato-oncology programme offers targeted treatment and long-term follow-up for blood cancers. For the small proportion of patients who do not achieve an adequate response to targeted therapy, allogeneic stem cell transplantation may also be considered when clinically appropriate.

The goal is to ensure that patients have access to the full continuum of CML care, from accurate diagnosis and treatment selection to regular molecular monitoring and timely changes in therapy when needed.

To consult a cancer specialist at Rajiv Gandhi Cancer Institute & Research Centre, call +91-11-47022222 or visit www.rgcirc.org.

Frequently Asked Questions

1. When is World CML Day 2026 observed?

World CML Day is observed every year on 22 September. The date, written as 9/22, reflects the involvement of chromosomes 9 and 22 in the genetic change that causes CML.

2. Is chronic myeloid leukaemia inherited?

Usually, no. The BCR::ABL1 genetic change associated with CML is acquired during a person’s lifetime rather than inherited from their parents.

3. Can CML be found before symptoms appear?

Yes. Some people with CML have few or no symptoms at first, and the condition may be suspected after a routine blood test shows an unusually high white blood cell count.

4. Why is molecular monitoring needed if treatment is working?

Because symptoms and routine blood counts do not show the full picture. Measuring BCR::ABL1 levels helps doctors assess how deeply the disease is responding to treatment and whether that response remains stable over time. (Nature)

5. Does everyone with CML need the same targeted therapy?

No. Several tyrosine kinase inhibitors are available, and the most appropriate option depends on the disease, treatment response, side effects, other health conditions and individual clinical factors.

6. Which specialist treats CML?

CML is usually managed by a haematologist or haemato-oncologist with support from pathology and molecular diagnostic teams. Regular follow-up is important because treatment decisions are closely linked to blood counts and molecular test results.

7. Which is the best hospital for CML treatment in Delhi?

For patients looking for the best hospital for CML treatment in Delhi, it is important to choose a centre that combines specialist haemato-oncology expertise, advanced molecular diagnostics, regular BCR::ABL1 monitoring and compassionate long-term care.

At RGCIRC, CML care brings together experienced haemato-oncologists, molecular diagnostics and coordinated follow-up to support patients at every stage of treatment. Our focus on clinical excellence, specialist expertise and empathy helps ensure that treatment decisions are medically precise while patients and families remain informed, supported and involved in their care.