Figure 1.

Approaches for investigating metabolic resistance in breast cancer patients. The CYP2D6-endoxifen relationship is well established. The endoxifen-efficacy relationship has been reported but not sufficiently validated due to a lack of available data. The CYP2D6-efficacy relationship has not been conclusively demonstrated due to the imprecision in using CYP2D6 as a surrogate of endoxifen concentration. Box plot and survival curves are for illustration purposes only. EM = Extensive Metabolizer, IM = Intermediate Metabolizer, PM = Poor Metabolizer.