A gene mutation may throw you off course
Some patients with Philadelphia chromosome–positive chronic myeloid leukemia (Ph+ CML) in chronic phase can develop what’s known as a gene mutation. A mutation is a change in the DNA of a cell.
 | Mutations may cause drug resistance
One of the goals of treatment for Ph+ CML in chronic phase is to see the number of leukemic cells in the blood go down. That may not happen for some people. If the number of leukemic cells in your body starts going up instead of decreasing, your doctor may want to see if you have become resistant to your medication. This is often called “drug resistance.” It occurs when cancer cells are not responding to a medication.
There are 2 types of drug resistance:
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Testing for a mutation in the BCR‑ABL1 gene
In Ph+ CML in chronic phase, one of the causes of drug resistance is a mutation in the BCR‑ABL1 gene.
Here are some reasons why your doctor may decide to have you tested for a gene mutation:
You are not responding or are no longer responding to a medication
You are unable to reach a treatment milestone
To determine if you have a mutation, your doctor may order a BCR‑ABL1 kinase domain mutation analysis. This test looks for mutations in the BCR-ABL1 gene that may cause certain tyrosine kinase inhibitors (TKIs) that treat Ph+ CML in chronic phase to stop working.
 | Identifying the T315I gene mutation
There are a number of different gene mutations that can occur in Ph+ CML in chronic phase, including a mutation called T315I. The only way to determine if you have a mutation is to undergo a BCR-ABL1 kinase domain mutation analysis. If this test shows that you have developed the T315I mutation, your doctor may consider whether to change your medication. SCEMBLIX is approved to treat Ph+ CML in chronic phase for those with the T315I mutation.
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 | Can you become resistant to your medication?
Over time, some people may stop responding to their medication for Ph+ CML in chronic phase. This may be caused by a gene mutation. If you aren’t seeing the results you had hoped for, ask your doctor if you should be tested for a gene mutation. |
