Adjuvant Treatment for High-risk Triple Negative Breast Cancer Patients With the Anti-PD-l1 Antibody Avelumab

* to determine whether 1 year of adjuvant Avelumab improves disease-free survival (DFS) compared to observation in patients with high-risk primary triple negative breast cancer who have completed treatment with curative intent including surgery of the primary tumor and neo- or adjuvant chemotherapy (Stratum A \[surgery of the primary tumor followed by adjuvant chemotherapy\] and Stratum B \[neoadjuvant chemotherapy followed by surgery\] combined). * to determine whether 1 year of adjuvant Avelumab improves disease-free survival (DFS) compared to observation in patients with high-risk primary triple negative breast cancer who have completed treatment with curative intent including neoadjuvant chemotherapy followed by surgery (Stratum B). * to determine whether Avelumab improves overall survival (OS) compared to observation in patients with high-risk primary triple negative breast cancer who have completed treatment with curative intent including surgery of the primary tumor and neo- or adjuvant chemotherapy. * to determine whether 1 year of adjuvant Avelumab improves disease-free survival (DFS) compared to observation in PD-L1-positive (as determined by a companion diagnostic test under development) patients with high-risk primary triple negative breast cancer who have completed treatment with curative intent including surgery of the primary tumor and neo- or adjuvant chemotherapy.