Although equivalent experimental systems have been employed in a variety of assessments to determine BCR-ABL1 kinase domain mutation sensitivity on the basis of IC50 values (89, 98), different incubation times and TKI concentration ranges have been used as ... Although equivalent experimental systems have been employed in a variety of assessments to determine BCR-ABL1 kinase domain mutation sensitivity on the basis of IC50 values (89, 98), different incubation times and TKI concentration ranges have been used as well as varying methods to measure cell viability and proliferation. Color-coded schemes to indicate TKI sensitivity based on in vitro analyses should be interpreted with clinical caution as in vitro findings cannot be directly extrapolated to the clinical setting. (Figure adapted from O'Hare et al. 89, © the American Society of Hematology). Dragana Milojkovic, and Jane Apperley Clin Cancer Res 2009;15:7519-7527 ©2009 by American Association for Cancer Research