Phases

The clinical course of CML is divided into three different phases: chronic, accelerated, or blastic. This classification helps doctors plan treatment and predict prognosis (chance of recovery).

Chronic phase. The blood and bone marrow contain less than 5% blasts (immature leukemia cells) in samples of blood and bone marrow. This phase often lasts for several years. About 90% of people are in chronic phase at the time of diagnosis.

Accelerated phase. In the accelerated phase, there are more than 5%, but less than 30%, blasts in both the peripheral blood and bone marrow, and these cells often have new cytogenetic changes, which develop as the CML cells gain more mutations (DNA damage) and grow faster.

Blastic phase (blast crisis). In the blastic phase, there are more than 30% blasts in the peripheral blood or bone marrow. It develops when the CML cells begin behaving like acute leukemia. Patients in blast crisis often have fever, malaise (feeling unwell), an enlarged spleen, weight loss, and other symptoms.

Without effective treatment, CML in all patients in chronic phase will move into blast crisis in an average of approximately five years after diagnosis. The time for the disease to move to blast crisis is generally shorter in patients who have certain specific findings at the time of diagnosis, including higher numbers of blasts or cells called basophils (a special type of white blood cell), chromosome changes in addition to the Philadelphia chromosome, significant elevations of the white blood cell count, or greater enlargement of the spleen.