How Do You Know If Treatment for Chronic Myeloid Leukemia Is Working?

If you have chronic myeloid leukemia (CML) and are being treated with targeted drugs , your doctor will check your blood counts, examine you, and do other tests like bone marrow biopsy and PCR (of blood and/or bone marrow). These check-ups will be at least every 3 months for at least the first year of treatment. They're done to see how well the CML is responding to the treatment you're getting. If you are taking your medicine correctly and the CML is not responding, you may be switched to another drug.

Studies have suggested that a fast response (within 3 to 6 months) is linked to better outcomes.

These are the ways doctors look for different kinds of responses to treatment:

Hematologic response

Hematologic 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.

• Complete hematologic response: Also called CHR, is when all your blood cell counts have returned to normal, there are no immature cells seen in your blood, and your spleen is back to a normal size. You have no symptoms of CML.

• Partial hematologic response: A partial hematologic response means that your blood counts are better, but there are still signs or symptoms of CML. It means your white blood cell count is less than half of what it was before treatment, your platelet count is still high, and/or your spleen has shrunk, but is still enlarged.

Cytogenetic response

This test is done on a sample of your bone marrow. It's done with either cytogenetics or FISH testing. These tests find altered (mutated) chromosomes. (They are discussed in Tests for Chronic Myeloid Leukemia.)

• A complete cytogenetic response (CCyR) is when no cells with the Philadelphia chromosome can be found in your bone marrow.
• A partial cytogenetic response (PCyR) is when 1% to 34% of the cells still have the Philadelphia chromosome.

• A major cytogenetic response (MCyR) means less than 35% of your cells have the Philadelphia chromosome. It includes both a complete and partial response.
• A minor cytogenetic response occurs when more than 35% of your cells still have the Philadelphia chromosome.

Molecular response

Molecular response uses the PCR test. It can be done on either your blood or bone marrow. It's based on the number of leukemia cells in your blood.

• A complete molecular response (CMR) means that the PCR test does not find the BCR-ABL gene in your blood.
• A major molecular response (MMR) means that the amount of BCR-ABL gene in your blood is 1/1000^th (or less) of what's expected in someone with untreated CML.
• An early molecular response (EMR) means that there is 10% or less BCR-ABL gene in your blood after 3 months and 6 months of treatment.

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