Chronic myeloid leukaemia

What is it?

Chronic myeloid leukaemia (CML) is a cancer of the bone marrow, where blood cells are made, and of the white blood cells it makes.^1,4 In CML, part of the DNA from one chromosome moves to another chromosome. This change is called the Philadelphia chromosome.⁴ The ABL1 gene joins the BCR gene to form the BCR::ABL1 fusion gene. This makes the bone marrow produce a protein that causes too many stem cells to become white blood cells.⁴ It develops slowly, over several years.¹

CML is rare.¹ It can start at any age, but it is more common from about 65 and rare in children; half of people are 67 or older when they find out.^1,4,5 The gene change is not passed on in families.⁴

The first signs

There may be no symptoms at first.²

• tiredness or weakness, and looking pale;²
• bruising or bleeding easily;²
• a swollen tummy, or pain or fullness under the left ribs;^2,4
• night sweats, fever, or losing weight without trying;^2,4
• getting ill often, bone aches or headaches.²

Less often, CML causes painful erections, or erections that do not go down.²

How doctors find out

Your family doctor examines you, looks for bruises and swellings, and may arrange a blood test.² A blood specialist (haematologist) then does more blood tests and a bone marrow biopsy: a small sample is taken with a needle, usually with a local anaesthetic.⁶ Genetic tests on your blood and bone marrow check for changes such as the Philadelphia chromosome. You may also have an ultrasound scan.^6,4 Results can take a few weeks.⁶ The tests show the phase of CML: chronic, accelerated or blast.⁶

Current treatment

Chronic-phase CML is treated with a tyrosine kinase inhibitor (asciminib, imatinib, dasatinib, nilotinib or bosutinib); a donor stem cell transplant is an option for some.Source: NCI PDQ

Will it get worse?

CML is usually treatable.¹ It has three phases, chronic, accelerated and blast, depending on how many immature cells (blasts) are in the blood and marrow.^6,4 How it goes depends on the phase, your age and your general health.⁴ With today's targeted medicines, more than 9 in 10 people with newly diagnosed chronic-phase CML are alive 10 years later, and most people are expected to live close to a normal lifespan.⁵

Medicines: what helps, and what to watch for

The main treatment is a group of targeted medicines called tyrosine kinase inhibitors (TKIs), such as imatinib, dasatinib, nilotinib, bosutinib or asciminib.^3,4,5 They aim to stop the cancer growing.³ Chemotherapy is used for some people, for example to control symptoms or in the blast phase.³

Good to know:

• There are many TKIs. If one gives you side effects or stops working, your specialist can switch you to another;³
• Some tests may be repeated to see how well the treatment is working. Decisions about whether to continue, change or stop treatment may be based on the results.⁴
• It is not yet clear whether TKIs can be stopped. People with a long, very deep response are the best candidates, but about half of those who stop see the leukaemia come back;⁵
• Weight-loss surgery may block some of the TKI tablets from being absorbed, so they may work less well.^4,5

A transplant, for some people

A stem cell transplant from a donor replaces damaged blood cells with healthy ones after strong chemotherapy.^3,4 It may be considered if TKIs stop controlling the leukaemia, or in the accelerated or blast phase.³ It is the only treatment that reliably cures CML: about half to 7 in 10 people who have it in the chronic phase seem to be cured.⁵

Is there a cure?

CML usually develops slowly and is usually treatable. With targeted medicines, most people are expected to live close to a normal lifespan.^1,5 A donor stem cell transplant can cure some people.⁵ Clinical trials are testing new treatments and new ways to use current ones.⁴

See the 190 trials you can join

Median survival

Expected to be close to a normal lifespan for most people with today's medicinesSource: NCI PDQ, 2025

Measured in: Most patients, with tyrosine kinase inhibitors (a projection)

Sources

Written in plain words by Frontlight from these pages:

1. NHS: Chronic myeloid leukaemia – What is chronic myeloid leukaemia?
2. NHS: Chronic myeloid leukaemia – Symptoms
3. NHS: Chronic myeloid leukaemia – Treatment
4. NCI PDQ: Chronic Myeloid Leukemia Treatment (PDQ®) – Patient Version
5. NCI PDQ: Chronic Myeloid Leukemia Treatment (PDQ®) – Health Professional Version
6. NHS: Chronic myeloid leukaemia – Tests and next steps