Health condition
CML treatment milestones
CML treatment is judged against molecular milestones - target BCR-ABL levels at 3, 6 and 12 months - which tell you and your team whether your tablet is working well enough or should be changed.
Why trust this guide
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Editorial team
Written by our editorial team from the UK sources listed on each page.
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Sourced from guidance
Checked against current NHS and UK specialist society guidance at the time of review.
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Current for 2026
Reviewed on 2026-09-27 with the next review scheduled for 2027-09-27.
Key facts
The essentials at a glance.
The symptoms to recognise, when to seek help, which specialist to see, and what treatment usually involves.
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BCR-ABL blood levels are measured on a standardised international scale
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Broad targets: 10% or less by 3 months, 1% or less by 6 months, 0.1% or less by 12 months
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Missing a milestone prompts a review of adherence, drug levels and mutation testing
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Deep, sustained responses open the door to discussing treatment-free remission
Understanding the condition
What it is and what happens next.
What causes it, how it is diagnosed, and the treatment routes available in the UK.
What it is and how it feels
Because CML has a single measurable driver, treatment success can be tracked with unusual precision. A blood test reports the amount of BCR-ABL transcript as a percentage. Falling levels confirm the tyrosine kinase inhibitor is working; the widely used milestones at three, six and twelve months separate optimal responses from warning signs that deserve closer attention.
Diagnosis and treatment routes
If a milestone is missed, the first questions are practical: are doses being taken consistently, and are interacting medicines or side effects getting in the way? If the response is genuinely inadequate, mutation testing helps choose an alternative inhibitor. Understanding your own numbers is empowering, and it is entirely reasonable to ask for your BCR-ABL results and trend at every clinic visit. If you are waiting for results or want a second opinion on a proposed plan, a private consultation with a specialist who treats this condition regularly can usually be arranged quickly, and most will review your existing scans, biopsy reports and MDT correspondence.
Seeing a specialist
Who to see, and how quickly you can be seen.
The specialist for this condition is usually a consultant haematologist. Your GP can refer you on the NHS, or you can arrange a private consultation directly.
A quiet reminder
This guide is for information, not medical advice.
Your GP knows your history and can tell you which parts apply to you. If in doubt, see them - and seek urgent care for any of the emergency symptoms described above.
Frequently asked
Common questions about CML treatment milestones.
Quick, plain-English answers to what people ask us most.
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What are treatment milestones in CML?
Treatment milestones in chronic myeloid leukaemia (CML) are specific, time-based targets used to assess how well a person is responding to targeted therapy, based on measuring levels of the abnormal BCR-ABL1 gene in the blood at set points after starting treatment, typically at 3, 6, and 12 months. Meeting these milestones is associated with better long-term outcomes, while missing them may prompt a change in treatment approach. This structured monitoring is a central feature of modern CML management.
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Why are these milestones important?
Research has shown that achieving specific reductions in BCR-ABL1 levels at these defined time points is strongly associated with better long-term disease control and outcomes, while failing to meet a milestone can indicate the current treatment isn't working optimally and may need to be changed. This allows your haematology team to identify and address suboptimal treatment response early, before it leads to disease progression. This proactive, milestone-based approach is one of the reasons outcomes in CML have improved so significantly.
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What happens if I don't meet a milestone?
If a milestone isn't met, your haematologist will typically investigate possible reasons, including checking whether you've been taking your medication consistently as prescribed, testing for specific mutations that might cause resistance to your current treatment, and considering whether switching to a different targeted therapy might achieve a better response. Missing an early milestone doesn't necessarily mean a poor long-term outcome, particularly if the treatment approach is adjusted appropriately. This is exactly why regular monitoring against these milestones matters so much.
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How is monitoring for these milestones done?
Monitoring relies on regular blood tests measuring the specific BCR-ABL1 gene levels using a sensitive molecular technique (quantitative PCR), typically performed at 3, 6, and 12 months after starting treatment, and then periodically thereafter to ensure the response is maintained. Consistent monitoring, ideally through the same laboratory using standardised methods, helps ensure reliable tracking of your specific trend over time. Your haematology team will explain your specific results in the context of these established milestones at each review.
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What does achieving a 'deep molecular response' mean?
A deep molecular response means the BCR-ABL1 gene level has fallen to a very low or undetectable level, representing an excellent response to treatment. Achieving and sustaining this level of response for a prolonged period is one of the key requirements considered when discussing whether treatment-free remission (safely stopping treatment) might eventually be appropriate for carefully selected patients. Not everyone who achieves this deep response will be eligible or choose to stop treatment, but it represents the best possible response category.
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When should I discuss my milestone results with my specialist?
Your haematology team will routinely discuss your specific results against these milestones at each scheduled follow-up appointment, so this is generally managed within your regular ongoing care rather than needing a separate referral. If you have concerns about your progress between appointments, contact your haematology team directly; a private haematology consultation can also be arranged within about 2 weeks if additional specialist input or a second opinion is wanted.