New data refine the risk estimates associated with various treatments As knowledge of the clinical and pathological subtypes of ductal carcinoma in situ (DCIS) grows, medical oncologists, surgical oncologists, and radiation oncologists have an increasingly complex task in diagnosing and treating this disease, and advising their patients on the best course of action. DCIS accounts for about one in five of all new cases of breast cancer in the United States each year (~60 000), and about two thirds of these are oestrogen receptor positive tumours (National Institutes of Health. State-of-the-science conference: diagnosis and management of ductal carcinoma in situ (DCIS). September 22-24, 2009, Bethesda, MA, USA). DCIS has the potential to progress to invasive breast cancer and confers an increased risk of ipsilateral and contralateral invasive breast cancer. The incidence of DCIS rose from 1.87 per 100 000 women in 1973-5 to 32.5 per 100 000 women in 2005. Incident increases were greatest in tumours with no necrosis within the DCIS, and although the increase was seen across all ages, it was greater in women over 50 years of age.1 2 3 The national surgical adjuvant breast and bowel project (NSABP) trials B-17 and B-24 have been of pivotal importance in assessing the association between local control, local and distant recurrence, new …