The results of three large clinical trials with focus on precision medicine in women with hormone receptor positive and HER2-negative breast cancer showed that postmenopausal women with high-risk features defined by standard clinical factors (tumor size, nodal status, malignancy grade), but at low risk of recurrence according to genomic assays, could safely be allocated to endocrine therapy alone, whereas a benefit of chemotherapy in premenopausal women was shown consistently17,19. The gene discussed is ERBB2; the disease is breast cancer.