[en] Background: After the results of prospective randomized trials, hypofractionated external beam radiotherapy replaced the conventional dose fractionation in women with early stage breast cancer after breast-conserving surgery. However, its efficacy and toxicity after mastectomy is still under evaluation and not routinely used. The aim of this study was to demonstrate our experience in using hypofractionated radiotherapy in breast cancer women, and evaluation of acute toxicity profile. Methods and materials: Between May and October 2016, all 55 consecutive women with breast cancer referred to the Oncology Service of the University Hospital Center “Mother Theresa”, received hypofractionated 3D conformal radiotherapy (40.5Gy in 15 fractions) via a Linear Accelerator of 6 and 18 MV. 23 patients were irradiated to the whole breast with an additional boost dose of 10Gy in 5 fractions at the tumor bed and 32 others to the chest wall. From all treated women, 33 of them were also irradiated concomitantly to the supraclavicular fossa. The dosimetric parameters and exposure to heart and lung were analyzed. Acute toxicity assessment was done based on RTOG toxicity criteria. Results: Hypofractionated radiotherapy was well tolerated by all patients, without interruptions. The mean age was 54 years (range 29-79 years) and 64% of women were postmenopausal. Early stage disease (Stage I and II) constituted 53%, while locally advanced 47%. The majority of patients (79%) had prior chemotherapy. The maximum radiotherapy dose received was on average 42.61Gy (range 41.84-43.38Gy). The mean lung dose was 7.39Gy and V20 was 16%. The mean V25 to the heart was 3.3% for left side and 0% for right side tumors. Acute toxicities were mostly skin toxicities of grade 1 in 73% of patients and grade 2 in 18% of them. Dysphagia and hematological toxicity grade 1 was seen in 2 and 3 patients respectively. No one had grade 3 toxicity. Conclusions: Hypofractionated external beam radiotherapy seems to be a feasible treatment for women with breast cancer not only after breast conserving surgery but also after mastectomy and treatment of supraclavicular fossa. It has shown low acute toxicities. However further follow-up is needed for better evaluation of patient’s outcome. Key words: Breast cancer, hypofractionation, radiotherapy, toxicity. (author)