Monitoring your response to chronic myeloid leukaemia (CML) treatment

The aim of treatment is to put your chronic myeloid leukaemia (CML) into remission. Remission means there are no signs of CML in your blood or bone marrow.

The doctors do regular tests to look for signs of CML. The test results provide information about how well the treatment is working. Doctors often refer to this as your ‘response to treatment’.

There are different ways that doctors look for signs of CML and measure your response to treatment. There are 3 types of responses:

• haematological response

• molecular response

• cytogenetic response

How do doctors measure your response to treatment?

When you start treatment, you have tests at regular time points. These tests are to see whether your CML is responding to treatment. 

Haematological response

Your haematological response is based on whether your ​blood cells​ go back to normal levels.

You usually have a high number of ​white blood cells​ when you are diagnosed with CML.

You have a full blood count every 2 weeks when you start treatment. The doctors look at your levels of ​haemoglobin​ , white cells and ​platelets​ to see if they go back to normal levels.

They also examine you to see if your ​spleen​ is a normal size.

Molecular response

Your molecular response is based on how much of the BCR-ABL1 gene a PCR test finds. PCR stands for a polymerase chain reaction (PCR) test. This is a type of blood test. 

This is the most sensitive test to measure your response to treatment. The PCR test can detect tiny amounts of the BCR-ALB1 gene even if other tests show no signs of CML. 

Read about the BCR-BL1 gene

You usually have a PCR test every 3 months to begin with. And then every 3 to 6 months after that depending on your situation.

Cytogenetic response

Your cytogenetic response is based on the number of ​bone marrow​ cells with ​Philadelphia chromosome​ . You would need to have a bone marrow test to measure your cytogenetic response. 

Read more about the Philadelphia chromosome

In the past you had regular bone marrow tests during treatment to measure your cytogenetic response. But this test isn't as common anymore. This is because the doctors can usually get the information they need from the PCR blood test. 

But in some situations they might suggest you have a bone marrow test to look at you cytogenetic response. For example, if:

• your doctor is concerned that your CML is progressing

• there are abnormalities in your routine blood tests 

Your doctor will discuss this with you.

Read about targeted drug treatment for CML

Understanding your test results

Your haematological response

A complete haematological response means:

• your white blood cell level goes back to normal

• your platelet count is normal

• the doctor can’t see any blast cells (undeveloped or immature blood cells)

• your spleen is a normal size

Most people have a complete haematological response within 3 months of starting ​tyrosine kinase inhibitors (TKIs)​ . 

Your molecular response

Your PCR test results show the number of cells that have the BCR-ABL1 gene. Doctors use an international scale to measure the results. There are different levels of molecular response (MR):

MR1 means that 10 or less out of every 100 cells (10% or less) have the BCR-ABL1 gene.

MR2 means that 1 or less out of every 100 cells (1% or less) have the BCR-ABL1 gene.

MR3 means 1 or less out of every 1,000 cells (0.1% or less) have the BCR-ABL1 gene - this is called a major molecular response.

MR4 means 1 or less out of every 10,000 cells (0.01% or less) have the BCR-ABL1 gene - this is called a deep molecular response.

MR5 means 1 or less out of every 100,000 cells (0.001% or less) have the BCR-ABL1 gene - this is also called a deep molecular response.

The PCR test is very sensitive. It will detect the BCR-ABL1 gene for many months after you start treatment. So it can take a long time to have a deep molecular response.

There are national guidelines for 'target' PCR results at different time points after you start treatment. But people with CML respond to treatment in different ways. Your doctor will use these guidelines. And they will also look at your response based on your individual situation.

Laboratories have different ways of doing the PCR test. So not all laboratories are able to detect extremely low levels of leukaemia. Your doctor will tell you more about PCR testing at your hospital. 

Your cytogenetic response

There are different levels of cytogenetic response. This depends on how many bone marrow cells contain the Philadelphia chromosome:

• complete cytogenetic response means none (or less than 1%) of the bone marrow cells contain Philadelphia chromosome

• partial cytogenetic response means between 1 and 35 out of 100 bone marrow cells (between 1 and 35%) contain Philadelphia chromosome

• minor cytogenetic response means between 36 and 65 out of 100 bone marrow cells (between 36 and 65%) contain Philadelphia chromosome

• minimal cytogenetic response means between 66 and 95 out of 100 bone marrow cells (between 66 and 95%) contain Philadelphia chromosome

• no cytogenetic response means more than 95 out of 100 bone marrow cells (more than 95%) contain Philadelphia chromosome

A complete or partial cytogenetic response are also sometimes described as a major cytogenetic response.

It takes longer to see a cytogenetic response than it does to see a haematological response. For example, it might take 6 months to see a complete cytogenetic response. This time varies for different people.

Your check ups

The most common treatment for CML is a type of targeted drug called a tyrosine kinase inhibitor (TKI). You'll have regular check ups if you're taking a TKI.

Your doctor or nurse checks for any side effects. It is important that you tell your doctor or nurse if you are having any problems taking your daily drug.

If your treatment stops working, your doctor or nurse will pick this up very quickly. There's likely to be other treatments you can try.

If you have had a transplant, initially the follow up appointments are twice a week and then weekly. After 6 months they will become less frequent if all is well.

Between appointments

Contact your doctor or specialist nurse if you have any concerns between appointments. You should also contact them if you notice any new symptoms. You don’t have to wait until your next visit.

Read about living with CML