Inclusion Criteria:  Written informed consent Aged 18-75 years old breast conservation surgery unilateral histologically confirmed invasive breast carcinoma or Ductal Carcinoma In Situ (DCIS) negative axillary lymph nodes or micrometastasis only Karnofsky Performance Status ≥80, and Life expectancy of >5 years Histologically negative surgical margin for invasive breast carcinoma or a minimum negative margin width of over 3mm for DCIS Surgery wound healed without infection ER (estrogen-receptor), PR (progesterone-receptor), HER2 (human epidermal growth factor receptor 2) and Ki67 testing can be performed on the primary breast tumor Female patients of child-producing potential must agree to use effective contraception for up to 1 month before study treatment and the duration of study participation  Exclusion Criteria:  Histological involvement of supraclavicular lymph node Histologically or radiologically confirmed involvement of ipsilateral internal mammary lymph nodes Pregnant or lactating women Severe non-neoplastic medical comorbidities Diagnosis of non-breast malignancy within 5 years preceding enrollment (excluding lobular carcinoma in situ, basal cell carcinoma of the skin, carcinoma in situ of skin and carcinoma in situ of the cervix, which are permitted). simultaneous contralateral breast cancer Previous radiotherapy to the neck, chest and/or ipsilateral axillary region Active collagen vascular disease Definitive histological or radiologic evidence of distant metastatic disease Evidence of T4 disease