CML does not have stages
For most cancers, staging is the process of finding out how far the cancer has spread. Most types of cancer are given stages of I, II, III, or IV, based on tumor size and how far from the original site in the body the cancer has spread. Stages are useful because they can help guide the healthcare team's decisions on appropriate treatment. Stages can also help determine disease prognosis (outlook).
The prognosis for someone with Ph+ CML depends on other information, such as the phase of the disease, as well as factors such as the age of the patient, blood count, and if the spleen is enlarged. So you will never hear a "stage" associated with Ph+ CML. And the "phase" does not tell the whole story.
What are the Phases of CML? (from NBC Health Video)