Words to know: Chronic myeloid leukemia (CML)
- Bone marrow
- The soft tissue inside bones where blood cells are made.
- Myeloid cells
- A family of blood cells made in the marrow, including many white blood cells. CML is a cancer of these cells.
- Philadelphia chromosome
- A shortened chromosome 22 formed when chromosomes 9 and 22 swap pieces. It is the hallmark of CML.
- BCR-ABL
- The joined gene created by the Philadelphia chromosome. It drives CML and is measured to track treatment.
- Tyrosine kinase inhibitor (TKI)
- A pill that blocks the BCR-ABL protein. Examples are imatinib, dasatinib, nilotinib, bosutinib, asciminib, and ponatinib.
- Chronic phase
- The early, most common phase of CML, with few blasts.
- Accelerated phase
- A phase where CML is getting harder to control.
- Blast phase
- An advanced phase where CML acts like an acute leukemia.
- Blasts
- Very young, immature blood cells. Many blasts mean more advanced disease.
- Spleen
- An organ on the upper left side of the belly that filters blood. It can become enlarged in CML.
- PCR test
- A very sensitive lab test that measures how much BCR-ABL gene is in your blood.
- International Scale (IS)
- A standard way to report BCR-ABL results as a percent, so results can be compared.
- Milestones
- BCR-ABL goals at 3, 6, and 12 months that show whether treatment is working well.
- Major molecular response (MMR)
- A BCR-ABL level of 0.1% or lower.
- Deep molecular response
- A BCR-ABL level of 0.01% or lower. It is needed before trying to stop a TKI.
- Cytogenetics
- A test that looks at chromosomes in cells under a microscope.
- Kinase domain mutation
- A change in the BCR-ABL gene that can make a TKI stop working.
- T315I
- A specific BCR-ABL mutation that only a few TKIs, such as ponatinib and asciminib, can treat.
- Treatment-free remission (TFR)
- Staying in remission after stopping TKI treatment, with close monitoring.
- Adherence
- Taking your medicine exactly as prescribed, every day.
- Pleural effusion
- Fluid around the lungs. It can be a side effect of dasatinib.
- Sokal and ELTS scores
- Risk scores at diagnosis that use age, spleen size, platelets, and blasts.
- Resistance
- When CML stops responding, or does not respond well, to a TKI.
- Allogeneic stem cell transplant
- A transplant using blood-forming stem cells from a donor. It is rarely needed for CML today.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.