How do you know if your CML treatment is working?

If you have chronic myeloid leukaemia (CML) and are being treated with targeted drugs, your doctor will check your blood counts, examine you, and do other tests, for example a bone marrow biopsy and PCR (Polymerase Chain Reaction) test (of blood and/or bone marrow). These check ups should happen at a minimum interval of every 3 months for at least the first year of treatment. They are done to see how well the CML is responding to your treatment.¹

Here’s are some quick explanations of how treatment response is measured:

• Haematological Response is based on the number of cells in your blood. The test used to measure this is a CBC or complete blood count. It's done on a sample of blood taken from your arm.²
• Cytogenetic Response is a response to treatment of CML that occurs in the marrow, rather than just in the blood. This test is done on a sample of your bone marrow. It's done with either cytogenetics or FISH (Fluorescence in situ hybridisation) testing. These tests find altered (mutated) chromosomes.²
• Molecular Response can only be measured using a PCR test, a very sensitive test which can be used to detect the presence of very low levels of specific genetic material (DNA).² 

You may hear the terms ‘long-term deep molecular response’ or ‘durable complete molecular response’. These both mean a long-lasting complete molecular response, which is the goal of CML treatment.²

If you are taking your medicine correctly and the CML is not responding, you may be switched to another drug.¹ Any change to your treatment will be fully explained to you by your doctor and discussed with you before a decision is made.

If you would like more details on the different responses, please also read Understanding your results.

1. 1. Yilmaz M, Jabbour E. Tyrosine Kinase Inhibitors Early in the Disease Course: Lessons From Chronic Myelogenous Leukemia. Semin Oncol. 2015 Dec;42(6):876-86. doi: 10.1053/j.seminoncol.2015.09.030. Epub 2015 Sep 24. PMID: 26615132; PMCID: PMC5473432.
   2. Yeung CC, Egan D, Radich JP. Molecular monitoring of chronic myeloid leukemia: present and future. Expert Rev Mol Diagn. 2016 Oct;16(10):1083-1091. doi: 10.1080/14737159.2016.1227243. Epub 2016 Sep 6. PMID: 27552202; PMCID: PMC5161535.