Blast phase may be present at diagnosis of CML, or it may develop after a period of chronic and/or accelerated phase CML.

Once diagnosed, the treatment approach for blast phase CML should be similar to that taken for acute myeloid leukaemia if in myeloid blast phase, or acute lymphoblastic leukaemia if in lymphoid blast phase, except that TKI therapy will generally be used alongside chemotherapy.

An allogeneic stem cell transplant is almost always indicated for patients with good performance status who achieve a second chronic phase.

The treatment pathway is complex for patients who are potential candidates for an allogeneic stem cell transplant. They should be admitted to a hospital with expertise in managing acute leukaemia that is accredited to undertake allogeneic stem cell transplants, or has close links to a hospital with this capability.