The following should be considered as contraindications for APBI: stage IIB–IV breast cancer, resection margins that cannot be microscopically assessed, extensive intraductal component (EIC), Paget’s disease or pathological skin involvement, age ≤ 40 years, triple-negative or HER2-positive phenotype and neoadjuvant chemotherapy in treatment history [23]. Here, ERBB2 is linked to breast cancer.