Patients with both clinical high-risk (CHR) and genomic high-risk (GHR) disease are assigned to receive chemotherapy. Patients with both clinical low-risk (CLR) and genomic low-risk (GLR) disease do not receive chemotherapy. Patients with discordant risk between the 2 decision-making tools (standard clinical-pathological criteria vs 70-gene signature criteria) are randomized to receive chemotherapy or not. Patients with HER-2 positive tumors which have both methods discordant and were randomized to no chemotherapy, can receive adjuvant trastuzumab alone or with adjuvant endocrine therapy (if hormonal receptor positive), if decided by the treating physician. Patients with HER-2 positive tumors that are classified low-risk by both methods can receive adjuvant trastuzumab alone or with adjuvant endocrine therapy (if hormonal receptor positive), if decided by the treating physician and if no issues for trastuzumab reimbursement exist in the investigator's country.