The FDA first approved neratinib in 2017 as an extended adjuvant therapy following the completion of one year of trastuzumab for early-stage HER2-positive breast cancer, based on the trial’s intention to treat the population, whereas the European Medicines Agency approved it only for HER2-positive early-stage breast cancer that is also HR+ and when it is started within 1 year of trastuzumab completion. This evidence concerns the gene ERBB2 and breast carcinoma.