Evolution of clinical trial endpoints in chronic myeloid leukemia: Efficacious therapies require sensitive monitoring techniques

The efficacy of tyrosine kinase inhibitors (TKIs) for chronic myeloid leukemia (CML) has brought treatment response assessment to the molecular level. Clinical trials endpoints for newer TKIs - such as major and complete molecular response - reflect the trend toward more-sensitive disease detection and deeper responses. Practice guidelines now formally define levels of response and link response benchmarks to outcome and treatment guidance. Efforts are ongoing to harmonize the methodology and terminology used to characterize molecular response. This review discusses the evolution of CML clinical trial endpoints in response to current therapeutic and monitoring modalities, and the implications of achieving molecular endpoints.