ERBB2 and breast cancer: Our models were trained and tested through cross-validation on two breast cancer cohorts: one with HER2-negative patients treated with chemotherapy (93 patients, referred to as the chemotherapy cohort) and another with HER2-positive patients treated with chemotherapy plus trastuzumab (61 patients, referred to as the trastuzumab cohort) (Sammut et al. 2022).