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Measuring Your CML Treatment Response

Your doctor needs to monitor your response to drug therapy for chronic myeloid leukemia with blood and bone marrow tests. This is a critically important step to under­take to bring your CML under control.

Your test results help your doctor decide whether to increase your drug dose to try for a better response, de­crease or stop the drug briefly because of side effects, change to a different drug or drug combination to better con­trol the CML, or change to a different drug or drug combination to manage side effects.

Measuring your CML treatment re­sponse is essential to controlling your disease. Your doctor measures your response using general treatment re­sponse guidelines for your first year of CML drug therapy. He or she regularly measures the number of red cells, white cells, platelets, and CML cells in your blood. Your doctor compares these num­bers with the results of the lab test done at the start of your treatment.

Testing Schedule
Your doctor may periodically examine your bone marrow. Your schedule for bone marrow testing might look like this:

• 6 and 12 months within the first year of diagnosis
• once or twice a year in the second year after diagnosis
• every 12 to 18 months once a good response is achieved

A marrow test is recommended when­ever a blood test indicates you’ve had a change in response to oral drug therapy.

A marrow test is recommended whenever a blood test indicates you’ve had a change in response to oral drug therapy.

Types of Response
Your doctor checks your progress to look for your response in the following areas: hema­tologic, cytogenetic, and molecular.

• Hematologic Response
  Hematologic Response Your doctor tests your blood for a complete blood count to measure the numbers of white cells, red cells, and platelets and the levels of hemoglobin (a protein in red cells that carries oxygen) and hemato­crit (the amount of blood that has red cells). A complete hematologic response means your levels of white cells, red cells, and platelets are normal or near normal.
• Cytogenetic Response
  You’ll undergo a bone marrow test to retrieve the cells that need to be examined. A fluorescence in situ hybridization (FISH) lab test measures the number of cells that have the Philadelphia (Ph) chromosome and the Bcr-Abl oncogene. A complete cyto­genetic response means no cells are detected with the Ph chromosome and Bcr-Abl oncogene.
• Molecular Response
  Your blood and bone marrow cells are examined to mea­sure the number of cells with the Bcr-Abl oncogenes using the extra sensitive poly­merase chain reaction (PCR) test. Your doctor looks for one of three responses. A partial molecular response means the number of cells with the Bcr-Abl oncogene has decreased. A major molecular response means there’s a 1,000-fold decrease in the level of cells with the Bcr-Abl oncogene from the level measured at the start of your treat­ment. A complete molecular response means the PCR test can’t detect any Bcr-Abl genes not found by FISH. The remaining CML cells that PCR can’t detect are called minimal residual dis­ease. Make sure your doctor uses the same laboratory each time for PCR test­ing since results can vary from lab to lab.

Desired Response
People with CML respond to treatment in different ways. Your baseline results (your test levels at the time of diagnosis) can influence your response. But your doctor will generally work with the following time frame as a guideline to achieve the de­sired response:

• a complete hematologic response and some cytogenetic improvement after 3 to 6 months of therapy
• a partial cytogenetic response of two-thirds reduction in the number of Ph chromosomes in the marrow after 6 to 12 months of therapy
• a complete cytogenetic response and partial molecular response after 12 to 18 months of therapy.

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