ABSTRACT
Defi ning responses to imatinib and other tyrosine kinase inhibitor (TKI) therapy and monitoring of patients with CML, have been a challenge for some time. Various efforts to defi ne failure and suboptimal responses have resulted in the two principal consensus panels, the European LeukemiaNet (ELN) and the MD Anderson Cancer Center (MDACC) panels, not necessarily mutually exclusive, which focus on achieving well-defi ned responses at specifi c time points (see chap. 8); others, such as the National Comprehensive Cancer Network (NCCN) chronic myeloid leukemia (CML) task force in the USA have also complied remarkably similar criteria. The initial goals of therapy are ideally to achieve a complete hematologic response (CHR) by three months and a complete cytogenetic response (CCyR) by 12 months. It is of some interest that slow responders who eventually achieve a CCyR may not necessarily have a signifi - cantly worse prognosis than those who achieve this landmark by the “ideal” 12 months period. This provides some rationale for continuing imatinib in patients who have not met the milestones stipulated in some of the current guidelines, such as the ELN, and do not have a useful alternative treatment available. Resistance to TKI therapy in general can be divided into primary and secondary. The issue of resistance is therefore clearly more complex than simply lack or loss of some predefi ned responses at specifi c times.
