Determining the phase of disease is a critical element of treatment planning and should be clearly documented in the patient’s medical record.

There are three phases of CML: chronic, accelerated and blast phase. They are described in more detail in the European LeukemiaNet 2020 recommendations for treating CML (Hochhaus et al. 2020).

More than 90 per cent of patients are diagnosed in the chronic phase (Hochhaus et al. 2017). The following tests are used to determine the phase of CML:

• investigations for extramedullary disease
• percentage of blasts, basophils and platelet count in the peripheral blood
• bone marrow morphology – a report should specifically state the phase of disease.

Patients with chronic phase CML should have their risk category assessed using an accepted scoring system. Currently, the EUTOS long-term survival (ELTS) score is preferred (Hochhaus et al. 2020).

The ELTS factors in age, spleen size, blasts in peripheral blood and platelet count to predict long-term survival and support treatment selection (European LeukaemiaNet 2020).