Chronic Phase CML Treatment
In the chronic phase of chronic myeloid leukemia (CML) the treatment goals are to:
- return the levels of blood cells to normal
- reduce or eliminate CML cells altogether
- preserve an acceptable quality of life
Three drugs, imatinib mesylate (Gleevec®), dasatinib (Sprycel®)and nilotinib (Tasigna®), have been approved as initial therapy for chronic phase CML and all three are reasonable options for newly diagnosed patients.
Gleevec is the oldest of the three treatments approved by the Food and Drug Administration to control CML. Gleevec is a type of drug called a Bcr-Abl tyrosine kinase inhibitor (TKI) that targets and blocks Bcr-Abl tyrosine kinase, the abnormal protein in cells that leads to CML.
Gleevec, Tasigna and Sprycel control CML for most people as long as they continue to take the drugs as prescribed. Patients who don't respond to usual doses may respond to a higher dose, but that may cause more side effects.
Gleevec, Tasigna and Sprycel offer benefits to CML patients that weren't available to them in the past:
- The drugs are taken by mouth and can easily be swallowed.
- They have decreased side effects when compared with former CML therapies, and the side effects are manageable.
- They do little damage to healthy tissues.
- Older patients tolerate them well.
- They have a very high response rate.
If Initial Therapy Doesn't Work
Depending on the drug you take as a newly diagnosed patient - Gleevec, Tasigna or Sprycel - your doctor may prescribe another TKI if:
- the drug can't control your CML (called drug resistance)
- you have strong side effects (called drug intolerance)
- the drug no longer works for you (called a loss of response)
If you're intolerant of or resistant to Gleevec, your doctor may prescribe Sprycel, which may work better for you. Sprycel blocks Bcr-Abl tyrosine kinase but binds to the abnormal protein differently than the other approved TKIs do. If you used Sprycel when you were newly diagnosed, and you became intolerant of or resistant to it, your doctor may prescribe Tasigna. Your doctor may also prescribe bosutinib (Bosulif®) or ponatinib (Iculsig®) which are TKIs that bind to the Bcr-Abl tyrosine kinase more effectively making them useful for many patients whose disease is resistant to Gleevec therapy. Omacetaxine (Synribo®), a proton synthesis inhibitor, is another FDA approved drug for patients. It is administered through injection under the skin.
Other CML Drug Therapies
Before the FDA approved Gleevec, Sprycel and Tasigna, other drugs such as interferon were the initial treatment for CML. If you're unable to tolerate or are resistant to TKIs, your doctor may suggest one of the following drugs instead; however, their side effects may be severe:
- interferon alpha (Roferon®-A and Intron® A)
- pegylated interferon alpha
- hydroxyurea (Hydrea®)
- cytarabine (Cytosar-U®)
- busulfan (Myleran®)
These drugs, or new treatment approaches, such as ponatinib (Iculsig®), or options in clinical trials, may be used to treat CML patients with a specific mutation (change) called T315I. This mutation changes the Bcr-Abl gene to make current TKIs ineffective.
If you would like to read about these drugs individually, including information about side effects, click here.
Measuring Your Treatment Response
TKI drug therapy doesn't cure chronic phase CML, but it brings about a stable remission (no signs or symptoms of the disease). Most patients being treated for CML can go about their day-to-day activities. Treatment usually returns blood cell levels to normal and the spleen to its normal size. Studies show that patients who've been treated with Gleevec since the drug has been on the market (2001) have been able to keep their chronic phase CML under control.
During your treatment, which can be indefinite, your doctor will continue to carefully check you for any signs that CML is returning (called a relapse). You'll need regular health checkups, including blood tests. From time to time, you'll need a bone marrow test.
Treatment in Older Adults
The first treatment choice for older adults who have chronic myeloid leukemia (CML) is the standard of care for all CML patients: targeted drug therapy with Gleevec, Tasigna or Sprycel. Because of their relatively mild side effects, these drugs are usually well tolerated by older adults. However, if you're not responding well to drug therapy, your doctor may suggest that you undergo a stem cell transplantation.