Résumé : The present invention relates to a method for determining sensitivity to a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor in a human subject having breast cancer, the method comprising determining in a sample from the subject the level of expression of 11 genes as defined in the claims. The present invention further provides kits of parts, nucleic acid arrays, and uses thereof for determining sensitivity to a CDK4/6 inhibitor in a human subject having breast cancer. The present invention also relates to methods of treating a human subject having breast cancer, comprising administering a therapeutically effective amount of the CDK4/6 inhibitor to the subject.