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Chronic Myeloid Leukemia (CML): Testing During Treatment

During treatment for CML, you’ll have tests to see how well the treatment is working. Your blood and bone marrow will be tested every 3 to 6 months. The tests look for the Philadelphia (Ph) chromosome. And they may also look for the BCR-ABL gene that almost all CML cells have. The testing is done to see if the treatment is destroying leukemia cells. 

The main goal of treatment is to reduce or remove cells with the Ph chromosome. This stops symptoms, and puts the cancer into remission. Remission means no signs of the disease in the body.

Your healthcare team may look for 3 types of responses the CML has to treatment. These include:  

  • Hematologic response

  • Cytogenetic response

  • Molecular response

What is hematologic response? 

This type of response means the levels of blood cells get better, and symptoms get better. This type of response most often occurs within a couple of months of starting treatment for chronic phase CML. The levels of hematologic response include: 

  • Complete hematologic response. Levels of blood cells return to normal. There are no CML cells seen in the blood. The spleen is a normal size. 

  • Partial hematologic response. Levels of blood cells have improved but have not fully returned to normal. Symptoms have improved but have not fully returned to normal.

What is cytogenetic response? 

This type of response means there is a change in the amount of cells with the Ph chromosome in the blood or bone marrow. The levels of cytogenetic response include: 

  • Minor cytogenetic response. Fewer cells with the Ph chromosome are found in the blood or bone marrow. But it’s still in 35% to 90% of the cells.

  • Major cytogenetic response. There are 35% or fewer cells with the Ph chromosome than at diagnosis. This term is sometimes used to describe either a complete or partial response.

  • Partial cytogenetic response. This is when 1% to 35% of the cells in the blood or bone marrow still have the Ph chromosome.

  • Complete cytogenetic response. No cells with the Ph chromosome are found in the blood or bone marrow.

What is molecular response?

This type of response shows if the BCR-ABL gene can still be found in the CML cells. The levels of molecular response include: 

  • Major. This means the level of BCR-ABL detected is very low.

  • Complete. This means the BCR-ABL gene can't be detected.

What your results mean 

Your healthcare team will explain what your test results mean for your treatment and your prognosis. If one type of treatment has no effect, or works for a while and then stops, your team may switch you to another type of treatment. Studies have shown that people with CML who have a complete or partial cytogenetic response tend to live longer than those who don’t. However, the leukemia may still come back in some people even after a complete cytogenetic response. This may be less likely after stem cell transplant. Talk with your healthcare team about what your results mean for you. 

Online Medical Reviewer: Alteri, Rick, MD
Online Medical Reviewer: Cunningham, Louise, RN
Date Last Reviewed: 9/30/2015
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