Ductal carcinoma in situ (DCIS)-precision medicine for de-escalation

Purpose of review Most women undergoing breast conservation surgery (BCS) for ductal carcinoma in situ (DCIS) receive breast radiotherapy (RT) to reduce the incidence of ipsilateral recurrent DCIS and development of invasive disease. This review seeks to appraise the potential for de-escalation of RT based on clinical, biomarker, and/or molecular testing. Recent findings Clinical prognostic factors have highlighted young age, tumor (DCIS) size, multifocality, DCIS grade, palpability, and immunohistochemical biomarkers (ER negative, HER2 positive) as prognostic factors. However, molecular markers including the Oncotype DCIS molecular assay alongside clinical factors and most recently the DCISionRT tool incorporating several biomarkers with clinical prognostic factors each appear to have the potential to guide clinical decision-making for the omission of RT. Refinements of these de-escalation tools are continuing. Conversely, markers to demonstrate which patients most need RT, which will then be effective to prevent further disease, are currently lacking. Selection of patients undergoing BCS for DCIS who might be suitable for de-escalation (omission) of RT has improved beyond use of a few clinical features to be guided by biomarker and molecular testing.