Accelerated partial breast irradiation (APBI) leads to a equivalent local control rate with lower toxicity as external beam irradiation (EBI) after breast conserving surgery (BCS) in a highly selected subgroup of patients with low risk invasive carcinoma and low risk duct carcinoma in-situ (DCIS). The goal of this trial is to assess the role of a modified dose of pulsed-dose-rate (PDR) and high-dose-rate (HDR) brachytherapy alone as Accelerated Partial Breast Irradiation (APBI) in a defined low-risk group of invasive breast cancer or ductal carcinoma in situ concerning local failure (all ipsilateral local recurrences), in particular regarding the local recurrences, the toxicity and for the cosmetic result. It is a phase II study. According to study protocol altogether 200 female patients will be treated.