Katy Hogben, MBBS, FRCS, PhD, talks about when and in what cases radiotherapy is used for the treatment of breast cancer at the 2016 World Congress on Controversies in Breast Cancer (CoBrCa) in Barcelona, Spain. She explains that in the UK, all women who have high risk or high grade DCIS and have a wide local excision will be offered radiotherapy as an adjunctive treatment. Women with a low risk or low grade DCIS won’t be offered radiotherapy. Furthermore, for the group of women with intermediate risk DCIS, radiotherapy will be discussed based on individual factors. These factors will include their age, size of the DCIS and the aggressiveness pathologically of the biopsy. Other risk factors such as whether the patient is a smoker are also taken into consideration. This is because there is an increased risk of lung cancer as a secondary cancer in smokers. She concludes that therefore treatment with radiotherapy is about individual decision making.