Chronic myeloid leukaemia (CML) treatment and side effects

When your blood counts return to normal, you’re said to have achieved a complete haematological response (CHR). This normally happens around three months after you start treatment.

A haematological response is measured using a full blood count. Although your blood counts will be within the normal range at this stage, there may still be leukaemia cells in your body that a full blood count can’t pick up, so you will need to continue having treatment to keep these levels under control.

To measure your cytogenetic response, your doctor will either take a bone marrow biopsy or run a polymerase chain reaction (PCR) test on a sample of your blood. These tests are more sensitive than a full blood count, so give doctors a better idea of the levels of leukaemia in your body.

A PCR test (done using a blood sample) is also used to measure your molecular response. If you’re responding to treatment, your doctor will usually take a blood sample and run a PCR test every three months. It’s a very reliable test that can detect one leukaemia cell in up to 100,000 normal blood cells.

PCR results are expressed as percentages. The results tell you what proportion of your blood cells are leukaemia cells.

Once you’ve achieved major molecular response (MMR), you’ll still have regular PCR tests. Tests are usually every three to six months to make sure you’re continuing to respond to treatment.

If no leukaemia cells can be detected you might hear your result referred to as ‘undetectable transcripts’. This means there may be an incredibly small number of leukaemia cells present somewhere in your body, but the test can’t pick these up. This is also called a complete molecular response (CMR) where your tests can’t detect any signs of CML and you no longer have disease symptoms.