Chronic myeloid leukaemia

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Chronic myeloid leukaemia at a glance

Chronic myeloid leukaemia, or CML, is a blood cancer driven by a joined gene called BCR::ABL1. It forms when parts of the BCR and ABL1 genes come together in a blood-forming cell. Most people are diagnosed in chronic phase, when the disease can often be controlled for many years with targeted tablets taken on a regular schedule. Taking treatment as prescribed is central to that control. Regular molecular testing measures the BCR::ABL1 signal in the blood to check the response.

CML is different from chronic lymphocytic leukaemia and from acute leukaemia. It does not usually follow a stage I-to-IV system. The key questions are the disease phase, the starting risk, the response to treatment and whether a medicine is both effective and tolerable. Some carefully selected people eventually attempt treatment-free remission, but stopping tablets is only safe within a specialist monitoring plan.

Symptoms and when to seek help

CML may be found on a routine blood count before symptoms occur. Tiredness, weight loss, night sweats, fullness after a small meal or discomfort under the left ribs can reflect an enlarged spleen. The white-cell count may be very high without the usual symptoms of an infection.

Severe breathlessness, chest pain, a new symptom affecting the brain or nerves, such as sudden weakness or confusion, major bleeding or a painful prolonged erection requires urgent assessment. These are uncommon but can be associated with very high counts or other serious problems. Once treatment starts, new breathlessness, fainting, severe abdominal pain or symptoms of a blood clot also need prompt advice because drug complications can require a change in management.

What to ask at the first visit

Ask whether CML is in chronic phase, which molecular test will be followed and why the proposed tablet suits your health. Tell the team about heart or lung disease, diabetes, blood pressure, pancreatitis (inflammation of the pancreas), pregnancy plans and all other medicines. The best first drug is the one that offers an appropriate balance of response, safety and a schedule you can follow reliably.

Making this information useful to you

A cancer diagnosis can arrive before you have had time to understand the tests. You do not need to learn every treatment name at once. Begin with the exact diagnosis, where the cancer is, and what the team recommends next. A relative or friend can join the appointment if you would find that helpful. Ask for an interpreter when language makes a discussion harder; important decisions should not depend on guessing unfamiliar words.

This guide explains possibilities, not a prescription for your situation. Your blood and tissue test results, scan findings, general health, previous treatment and priorities determine which possibilities apply. Two people with the same cancer name may appropriately receive different treatment. If a recommendation differs from something you have read, ask the team to explain the reason and the evidence behind it.

Keep a list of medicines, allergies and other health conditions, including non-prescription products, vitamins and herbal remedies. Tell the team about previous cancer treatment, pregnancy or breastfeeding, and anything that could affect attending appointments. Do not stop an established medicine without advice. Bring your questions in the order that matters most to you, so that the most important concern is discussed first.

Understand

The Philadelphia chromosome and BCR::ABL1

In most CML, pieces of chromosomes 9 and 22 exchange places. This creates the Philadelphia chromosome and joins the BCR and ABL1 genes. The resulting protein acts like a growth switch that is persistently active. Tyrosine kinase inhibitors, or TKIs, interrupt that signal.

This change is usually acquired in the blood-forming cells during life. It is not generally inherited from a parent and is not usually passed to children. CML is not contagious. Finding BCR::ABL1 explains the mechanism of the disease, but it does not identify something you did to cause it.

Different kinds of response

A haematological response means that blood counts and related clinical findings improve. A cytogenetic response means that fewer cells carry the Philadelphia chromosome. A molecular response means that the measured BCR::ABL1 signal falls. These are related but different measures.

Quantitative polymerase chain reaction (PCR) is a sensitive test that measures the BCR::ABL1 signal. Its results are often reported on the International Scale. A major molecular response, or MMR, corresponds to BCR::ABL1 of 0.1% or lower on that scale. Deeper molecular responses include MR4, at 0.01% or lower, and MR4.5, at 0.0032% or lower. These are laboratory response levels, not cancer stages. A result described as undetectable depends on how sensitive that particular sample and test were; it does not prove that every CML cell has disappeared.

Tests and diagnosis

Confirming CML

A full blood count and blood film show the pattern of raised and immature white cells and any changes in red cells or platelets. BCR::ABL1 testing confirms the defining abnormality. Bone marrow examination and chromosome analysis are commonly used at diagnosis to assess phase and look for additional chromosome changes.

The laboratory identifies the transcript type, the particular form of the BCR::ABL1 message, so that subsequent PCR testing measures the right target. Rare transcripts may need a specialist laboratory and may not fit standard International Scale reporting. Ask that the baseline result and transcript are recorded clearly, especially if future blood tests will be performed elsewhere.

Baseline safety assessment

Kidney and liver function, blood pressure, blood sugar and cardiovascular risk are assessed before treatment. An electrocardiogram (ECG), which records the heart’s electrical activity, and other heart tests may be needed for certain drugs. Lung symptoms, previous fluid around the lungs, blood-vessel disease and pancreatic problems are particularly relevant to selecting a TKI.

Tell the team about acid-reducing medicines, antibiotics, antifungals, anti-seizure medicines, supplements and herbal products. Some change TKI absorption or blood levels. A pharmacy interaction review should be repeated when a new medicine is prescribed, not only at the first visit.

Molecular monitoring

PCR is usually checked about every three months early in treatment, with the interval adapted after a stable response. Results are interpreted as a trend. A small isolated fluctuation may reflect normal test variation, whereas a confirmed rise or loss of response needs a closer review.

Milestone assessments commonly occur around three, six and twelve months. The team compares the result with guideline targets while considering the starting level, treatment interruptions, side effects and adherence. Missing a milestone does not automatically mean immediate progression, but it should prompt an explanation and a plan.

Using the same quality-assured laboratory where possible makes comparisons easier. If the laboratory changes, provide the earlier reports. Blood-count improvement cannot replace PCR monitoring because the molecular response may change before symptoms or ordinary counts do.

When more testing is needed

If response is inadequate or is lost, the team first reviews missed doses, interactions and interruptions. BCR::ABL1 kinase-domain mutation testing may identify resistance and guide another drug. A marrow test may be needed if there are signs of progression or additional chromosome abnormalities.

The T315I mutation is one important resistance finding, but other mutations also matter. Some medicines overcome particular mutations while others do not. A mutation result should be matched to current treatment options and the person's cardiovascular and other risks rather than read as an automatic prescription.

Preparing for your appointment

If scans have been performed, bring a CD containing your scan images in Digital Imaging and Communications in Medicine (DICOM) format, the standard used for medical images, together with the software needed to view them, along with the written scan reports. Bring your biopsy report and ask whether the pathology slides or tissue blocks are needed for specialist review or additional tests. Keep originals safe and agree how borrowed material will be returned. Having the actual images allows the team to compare changes and plan treatment accurately.

A repeat test is sometimes needed because an earlier sample was too small, a scan did not cover the necessary area, or a new result will change treatment. Ask what question the test will answer, how it may affect the plan, and when you should expect the result. A result described as uncertain does not automatically mean the cancer is worse. Sometimes discussion between the scan specialist (radiologist), tissue specialist (pathologist) and treating team resolves the uncertainty without another procedure.

Before a scan or procedure, mention kidney problems, previous contrast reactions, implanted devices, diabetes medicines, blood-thinning medicines and the possibility of pregnancy. Follow the testing centre's instructions about food, drink and medicines. If you have not received those instructions, contact the centre rather than making changes yourself.

Planning your treatment

Choosing a targeted tablet

Initial options in chronic phase include imatinib, dasatinib, nilotinib, bosutinib and asciminib in appropriate patients. They differ in response speed, side effects, food instructions and interactions. A faster deep response may be valuable, but avoiding a serious drug complication is equally important.

Imatinib has a long record of effective use. Some newer TKIs produce deep responses more quickly, which may matter for higher-risk disease or a future treatment-free-remission goal. The choice is individual. The most potent option on paper is not always the best option for someone with particular heart, lung or vascular disease.

A sustainable daily routine

Because treatment is often long term, discuss how tablets fit around meals, work and other medicines. Use the exact instructions for the prescribed product. Some require fasting periods; others are taken with food. Do not crush or alter tablets unless the team or pharmacist has specifically advised it.

If a dose is missed or vomited, follow the medicine-specific instructions rather than doubling the next dose. If nausea, diarrhoea or difficulty obtaining a refill makes it hard to take treatment as planned, tell the team early so the problem can be addressed. Long gaps can reduce disease control even when you feel well.

Pregnancy and fertility planning

Discuss pregnancy plans before conception. TKIs may harm a developing baby, and stopping treatment without a plan can allow CML to return. Women considering pregnancy need an individual strategy based on response, timing and safe monitoring; interferon may be considered in selected circumstances under specialist care.

Advice for men taking TKIs can differ from advice for women, and it depends on the drug and circumstances. Ask about contraception, breastfeeding and fertility rather than assuming that all tablets have the same restrictions. An unexpected pregnancy warrants prompt contact with the haematology and obstetric teams, without making unsupervised treatment changes.

Questions to ask your care team

• What is the exact blood cancer type and risk category, and are any important results still pending?
• Is the aim to cure the cancer, reduce the chance of recurrence, control it, or relieve a particular symptom?
• What benefit do you expect from this option, and what are the reasonable alternatives for me?
• How will treatment affect everyday activities, fertility, sexual health and the things I most value?
• How will we know whether it is working, and when will we review the plan?
• Who should I contact between visits, including at night or over a weekend?

Clinical trials and newer treatments

A clinical trial can be worth considering at diagnosis or when treatment needs to change. Trials ask a defined question; some compare established treatments and others study a newer approach. Eligibility depends on the cancer, previous treatment, test results and health. Taking part is voluntary, and choosing not to participate does not remove your right to standard care. Ask about extra visits, possible randomisation (allocation to a treatment group by chance), travel, side effects and what happens when the study ends.

Newer treatments are considered using the clinical evidence, recognised guidelines and the exact cancer type, biomarkers (features found by laboratory tests) and previous treatment. Some options have less mature evidence than established treatments. Ask what is known, what remains uncertain and whether a clinical trial would be appropriate.

Your priorities and supportive care

Tell the team what you are hoping treatment will make possible: returning to work, caring for family, keeping independence, reducing pain or attending an important event. These priorities can influence a choice between reasonable options. If the likely benefit is small and the burden is substantial, discussing a less intensive approach is appropriate. Decisions can be revisited when your health or circumstances change.

Supportive and palliative care help with symptoms, sleep, mood, family concerns and planning. They can be provided alongside treatment intended to cure or control cancer. A referral does not mean that active treatment is ending. If the cancer cannot be cured, ask what treatments may help you live longer or more comfortably and how their burdens compare with their likely benefits.

Treatment options

First-line treatment in chronic phase

TKIs are the main treatment. They suppress the BCR::ABL1 signal so that normal blood production can recover. A short course of a count-lowering medicine may be used while diagnosis or definitive treatment is being arranged when white cells are very high. This temporary measure does not replace a long-term TKI strategy.

Imatinib, dasatinib, nilotinib and bosutinib bind the kinase in related ways but have different toxicity profiles. Asciminib targets a different part of the ABL1 protein and is an option for appropriately selected newly diagnosed or previously treated chronic-phase CML. The phase, mutation findings and product-specific indication must match the proposed use.

The first few weeks may involve more frequent blood counts and chemistry tests. Low counts can reflect treatment effects on the diseased marrow and may require a supervised pause or adjustment. The aim is an effective dose that can be sustained safely, not simply the highest possible dose.

Changing treatment for side effects

A patient may need a different TKI even when the CML is responding well. Persistent diarrhoea, troublesome fluid retention, pleural effusion (fluid around the lungs), changes in blood sugar or cholesterol, or blood-vessel risks can make the current drug unsuitable. Sometimes supportive treatment or dose adjustment is sufficient; sometimes switching is safer.

Changing because of intolerance is different from changing because of resistance. Ask which applies, whether another drug is expected to remain effective and what new monitoring will be needed. Do not accept disabling symptoms as inevitable without discussing them.

Changing treatment for inadequate response

If the BCR::ABL1 level has not fallen as expected, the team checks adherence, interactions, dose interruptions and test trends. Resistance mutation testing can then guide selection of a different TKI. The choice also depends on previous drugs and their side effects.

Ponatinib is important in specified resistant disease, including appropriate T315I-positive CML, but blocked arteries, which can cause a heart attack or stroke, and other serious risks require careful assessment and dose planning. Asciminib can be useful in appropriate resistant or intolerant chronic-phase disease, including some mutation-defined settings with a different dosing approach. Neither should be selected only because it is newer.

A donor transplant may be considered when suitable TKIs no longer provide control or when advanced disease develops. Referral should occur early enough to assess options rather than waiting until every aspect of the disease is unstable.

Advanced-phase CML

Advanced disease requires reassessment of the marrow, which blood-cell family is involved, and gene changes that may cause resistance to treatment. Blast-phase treatment often combines a suitable TKI with an acute-leukaemia-style programme. A lymphoid blast phase may require treatment similar to acute lymphoblastic leukaemia (ALL), including treatment to protect the brain and spinal cord; a myeloid blast phase follows a different approach.

For suitable patients, the aim may be to regain control and proceed to an allogeneic stem-cell transplant, using blood-forming cells from a donor. Transplant carries substantial risks but can offer a route to durable control when targeted tablets alone are insufficient. The plan should be made in a centre experienced in advanced CML and transplantation.

Treatment-free remission

Treatment-free remission, or TFR, means maintaining control after a planned TKI stop. It is considered only in selected chronic-phase patients with a sustained deep molecular response, sufficient prior treatment, an appropriate disease history and access to reliable frequent PCR testing. The criteria are stricter than simply having a normal blood count or one undetectable result.

PCR monitoring becomes especially frequent after stopping. Depending on the specialist protocol, this may mean testing every four to eight weeks at first, with longer intervals only after a stable response. Long-term monitoring continues even after years without tablets. Molecular recurrence often occurs before symptoms.

Loss of major molecular response generally leads to prompt restarting under the team's instructions; treatment should not be delayed while waiting for a second confirmatory result. Most patients who restart can regain a response, but this must not be treated as a reason to stop without supervision.

Some people develop muscle or joint pain after stopping a TKI. Others feel better without daily treatment. Both should be discussed. Needing to restart after a TFR attempt is not a personal failure and does not mean that earlier treatment was wasted; the principal goal remains safe disease control.

The limited role of other treatments

Chemotherapy and donor transplantation are not routine first treatment for most chronic-phase CML now that effective TKIs are available. Interferon has a role in selected circumstances, including some pregnancy-related plans. Radiotherapy or surgery is rarely needed for the leukaemia itself and is directed at particular complications rather than used as a standard CML pathway.

Managing side effects

Drug-specific safety concerns

Imatinib can cause fluid retention, cramps, nausea and changes in blood counts. Dasatinib can cause fluid around the lungs and, less commonly, raised pressure in the blood vessels of the lungs. New cough, breathlessness or reduced exercise tolerance should be assessed, even after a long period on treatment.

Nilotinib can affect blood sugar, cholesterol, heart rhythm and arterial risk. Bosutinib commonly causes diarrhoea and may affect liver tests. Asciminib can cause low counts, high blood pressure and pancreatic effects, among other problems. Ponatinib requires particular attention to vascular events, blood pressure and pancreatic or liver toxicity. This is not a complete side-effect list; ask for advice for your actual medicine.

When to contact the team urgently

Chest pain, sudden breathlessness, one-sided weakness, loss of vision, a painful cold limb or collapse requires emergency care. Severe upper abdominal pain, persistent vomiting, jaundice or fainting also needs prompt assessment. Report fever when counts are low and follow the team's threshold for urgent contact.

Do not stop and restart a TKI repeatedly to manage symptoms without discussing the pattern. Supervised adjustment allows the team to preserve disease control and identify whether a side effect is drug-related or has another cause.

Everyday symptom management

Take anti-sickness or bowel medicines only as advised, because some can interact with TKIs or affect heart rhythm. Maintain hydration during diarrhoea, with advice adapted to kidney or heart disease. Report diarrhoea that is persistent, bloody or associated with dizziness or reduced urine.

Muscle cramps, fatigue and sleep problems may improve with supportive measures, but significant symptoms deserve assessment. A diary of timing, meals and medicines can help identify patterns. Regular blood pressure checks and management of diabetes, cholesterol and smoking are part of safe long-term CML care, not separate concerns.

Keeping treatment manageable

Keep the team's contact details available and know where to go outside clinic hours. Report side effects early rather than waiting until the next appointment. A short record of symptoms, temperature, fluid intake and medicines can help the team decide what is needed. Do not change cancer medicine doses, restart a stopped treatment, or use leftover antibiotics without instructions. A planned delay or dose adjustment can be an important part of safe treatment.

If you receive treatment that can lower white blood cells, a temperature of 38°C (100.4°F) or higher needs urgent advice. Follow any lower threshold or additional instructions your team gives you. Chills, sudden weakness, confusion or feeling very unwell also need urgent assessment, even without a fever. Do not wait for a blood test appointment or try to hide the fever with medicine before speaking to the team.

Severe breathlessness, chest pain, a new seizure, sudden weakness, heavy bleeding or collapse require emergency care. New severe back pain with leg weakness, numbness around the bottom, or loss of bladder or bowel control also needs immediate assessment. Contact the nearest emergency service when necessary; a website contact form or routine messaging service is not an emergency pathway.

Eating, drinking and energy

Treatment may change appetite, taste, bowel habits and energy. Small, frequent meals and foods containing protein can be easier than large meals. Ask for dietitian support if weight is falling, swallowing is difficult, or you are avoiding many foods. There is no single diet that treats cancer, and severe restriction or prolonged fasting can make it harder to tolerate treatment. Check supplements with your team because some interact with medicines.

Take anti-sickness medicine as prescribed and report vomiting that prevents you keeping down fluids or essential medicines. Seek advice for persistent diarrhoea, dizziness, very little urine or increasing weakness. Fluid recommendations may need adjustment if you have heart or kidney disease. Mouth ulcers, pain or infection that interferes with eating should be treated promptly rather than accepted as unavoidable.

Gentle movement, short walks and planned rest may help fatigue, but activity should match your condition and any surgical or bone-safety restrictions. Fatigue can also reflect anaemia, infection, hormone changes, pain, poor sleep or low mood. Let the team assess a marked or persistent change. Accepting help with shopping, transport or meals can conserve energy for the activities that matter to you.

Live well

Long-term follow-up

Many people with well-controlled chronic-phase CML continue work, family activities and exercise. The exact outlook depends on response and other health conditions. Continue PCR tests even when life feels normal, because molecular monitoring is how the team confirms that the treatment remains effective.

Keep a record of the TKI, dose, transcript type, PCR results, major side effects and any resistance mutation. Bring this information if you move or receive care elsewhere. A change in tablet brand or formulation should be checked with the pharmacist, especially if food instructions or other medicines differ.

Planning travel, work and routine care

Before travel, arrange an adequate medicine supply, a plan for time zones and a way to obtain urgent advice. Do not place all essential medicines in checked luggage. Discuss whether the timing of a PCR test or a recent treatment change makes travel inconvenient or unsafe.

Dentists, surgeons and other prescribers should know about CML and the current drug. Some procedures or medicines require temporary adjustments, but those should be coordinated with the haematology team. Vaccination and routine health screening remain important, with individual advice if counts are low or treatment has changed.

Living with a condition that others cannot see

Daily tablets and repeated blood tests can be tiring even when there are few visible signs of illness. It is reasonable to ask for help with persistent fatigue, anxiety before PCR results or concerns about relationships and pregnancy. The absence of hospital infusions does not make those concerns less valid.

Ask the team to explain results in a consistent way, using the trend and the treatment goal. A small laboratory change should not dominate every aspect of life, but it should be interpreted by the team rather than ignored. Shared decisions can include tolerability, the possibility of future TFR and what matters most to you now.

Emotional and practical support

Feeling frightened, angry, sad or uncertain is understandable. You do not have to appear positive all the time. Ask about counselling, psycho-oncology (support for the emotional effects of cancer), support groups or a social worker if worry is affecting sleep, relationships or daily life. Persistent depression, panic or thoughts of self-harm need prompt professional help. Caregivers may need their own support and breaks; one person should not have to manage every appointment and household task alone.

It can help to agree who will update relatives and how much information you want shared. Children usually benefit from honest, age-appropriate explanations and reassurance about who will care for them. Ask permission before discussing private medical information with others. If concentration or memory is difficult, use reminders, a calendar and a trusted companion at important consultations.

Relationships, fertility and sexual health

Cancer and treatment can affect desire, comfort, fertility, body image and confidence. These are valid medical concerns. Raise fertility questions before treatment when possible, because some protective options need to be arranged early. The right approach depends on age, the treatment and how urgently it must start. Do not assume that absent periods or reduced fertility means pregnancy is impossible. Ask about contraception and the safe timing of pregnancy for your specific medicines.

Explain any pain, dryness, erection difficulties or changes in intimacy to the team. Appropriate treatments, rehabilitation and counselling can help. You can choose how much to involve a partner. Advice about hormone-containing treatments needs to take the cancer type and treatment into account; do not start them without discussing suitability.

Planning ahead while living well

Ask for a clear follow-up plan and know which symptoms should be reported between visits. Continue care for other conditions and discuss vaccinations with your oncology team; the timing and suitability of live vaccines can change during treatment. Avoid tobacco and ask for practical cessation support if needed. Activity, food and sleep plans should be realistic for your health rather than another source of pressure.

If treatment is long term, arrange periodic discussions about what is helping, what is difficult and what you want next. Planning for future care can protect your preferences and reduce uncertainty for family. You can discuss who should help with decisions if you become too unwell to speak for yourself, while continuing treatment and everyday life now.

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