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.

If you are taking your medicine correctly and the CML is not responding, you may be switched to another drug.

Hematological 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.

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.

Molecular responses 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). 

You may hear the terms long-term deep molecular response or a durable complete molecular response. This is a long-lasting complete molecular response. This is the goal of CML treatment.

The illustration below shows the estimated tumor size at diagnosis and during treatment1:

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