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Chronic Myeloid Leukemia (CML): Measuring Treatment Response

During treatment for CML, you’ll have tests to see how well the treatment is working. Your blood and bone marrow will likely be tested every 3 to 6 months. The tests look for the Philadelphia (Ph) chromosome. 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. It shows how well treatment is working.

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

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

  • Hematologic response

  • Cytogenetic response

  • Molecular response

What is a hematologic response? 

This type of response means the levels of red blood cells, white blood cells, and platelets get better. It also means that the symptoms get better too. This type of response most often occurs within a couple of months of starting treatment. 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 are still present.

What is a cytogenetic response? 

This type of response means there is a change in the number 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 percent to 90 percent of the cells.

  • Major cytogenetic response. There are 35 percent 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 one percent to 35 percent 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 a molecular response?

This type of response shows if the BCR-ABL gene can still be found in the blood or bone marrow. 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.

  • Early molecular response. This is done at 3 and 6 months after treatment starts. It means that at 3 and 6 months, the BCR-ABL gene is found in less than 10 percent of the cells. 

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. Talk with your healthcare team about what your results mean for you. 

Online Medical Reviewer: Levy, Adam S, MD
Online Medical Reviewer: Stump-Sutliff, Kim, RN, MSN, AOCNS
Date Last Reviewed: 6/1/2018
© 2021 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare provider's instructions.
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