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What Happens Once CML Treatment Begins?

Answers from the NCCN Guidelines for Patients™


Photo by Cancer Type

Testing Your Response to Treatment
To assess your response to treatment for chronic myelogenous leukemia, you will need to undergo blood and marrow tests before and during treatment. These tests include complete blood count (CBC), cytogenetic analysis, and quantitative polymerase chain reaction (QPCR). How often you will need these tests depends on the time since your treatment started and your previous test results. There are three different types of response to medications:

  • A hematologic response is a return of blood cells to normal levels and a decrease of blast cells and other immature cells in peripheral blood.
  • A cytogenetic response is a decrease in the number of Philadelphia chromosomes during metaphase cell division as measured by bone marrow aspirate and cytogenetic tests.
  • A molecular response is a decrease in the amount of BCR-ABL messenger RNA (mRNA) as measured by QPCR.

If you are not having an adequate response to treatment, you will be tested to see if your body is resistant to the medication. You may have primary resistance. Primary resistance to imatinib is not fully understood. It may be due to low levels of imatinib in the blood, but the NCCN Guidelines Panel does not recommend routine blood testing since there are no data to support that changing treatment based on plasma imatinib levels will improve results. Primary resistance may also be caused by abnormal activity of drug transporters that are lowering the level of imatinib. The overactivity of the multidrug resistance gene (MDR1) and underactivity of human organic cation transporter-1 (hOCT1 ) may be involved in primary resistance to imatinib.

If you are not having an adequate response to treatment, you will be tested to see if your body is resistant to the medication.

Secondary resistance to medications occurs in people who are already on the drug. The most common reason for secondary resistance is the restart of BCR-ABL gene activity. This occurs most often by mutations in the part of the BCR-ABL gene involved in making tyrosine kinase. However, mutations in other chromosomes may also cause secondary resistance. Among the mutations affecting tyrosine kinase, the presence of the T3151 mutation creates the highest resistance to imatinib, dasatinib, and nilotinib.

Not all cancer cells are alike. Some cancer cells are killed easily. Others survive due to clonal evolution and continue to multiply. Over time, they make up larger and larger numbers of the cancer cells since the other cells die. Clonal evolution commonly occurs in people who are resistant to imatinib.

When Can I Stop Taking My Medication?
Since drug treatments for CML do not cure, CML is a chronic disease and needs to be treated throughout life. You may be tempted to skip taking your medications or stop taking your medications altogether, especially if you feel well and have responded to treatment. However, not taking your medication as the doctor instructed can have harmful results. It is important to follow your doctor’s instructions to get the best results. If you are having trouble taking your medication, talk with your doctor. Your doctor may have important information for you to consider.

Controlling Symptoms
While the focus is on treating your CML, maintaining your quality of life is also a very important goal. Don’t hesitate to talk with your cancer care team about symptoms, especially any symptoms that make it hard for you to take your medications. There are effective and safe ways to treat symptoms of CML and most of the side effects caused by CML treatments. When properly given, medications can relieve symptoms without causing other symptoms. Symptom relief can help some people be more active and may, indirectly, help them live longer.

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You can view the full version of the NCCN Guidelines for Patients™: Chronic Myelogenous Leukemia at

Reproduced with permission from the NCCN Guidelines for Patients™: Chronic Myelogenous Leukemia V.1.2011 © 2011 National Comprehensive Cancer Network, Inc. All rights reserved. The NCCN Guidelines for Patients™ and illustrations herein may not be reproduced in any form for any purpose without the express written permission of the NCCN. To view the most recent and complete version of the NCCN Guidelines for Patients®, go online to NATIONAL COMPREHENSIVE CANCER NETWORK®, NCCN®, NCCN GUIDELINES™, and all other NCCN Content are trademarks owned by the National Comprehensive Cancer Network, Inc.

This article was published in Coping® with Cancer magazine, November/December 2011.