Facts and uncertainties in monitoring treatment response in chronic myeloid leukaemia.

For patients with chronic myeloid leukaemia (CML), current guidelines advocate frequent monitoring using haematological, cytogenetic, and molecular methods, and these have been used to set targets for disease responses at various time points. Recent clinical data, however, have provided new information on responses to treatment with tyrosine kinase inhibitors, which may have implications for how patients should be monitored. Topics of debate include whether time to complete cytogenetic response (CCyR) is clinically important, what benefit is derived from achieving a major molecular response in patients who have achieved CCyR, and what prognostic implications are associated with developing different types of BCR-ABL mutation. Here, current questions relating to CML monitoring are addressed and practical interpretations are suggested.