DCIS: Risk Assessment in the Molecular Era.

Ductal carcinoma in situ (DCIS) represents 20% of all breast cancers. The treatment paradigm for the majority of patients with DCIS consists of breast-conserving surgery (BCS) and radiotherapy (RT), with adjuvant endocrine therapy offered for hormone-receptor positive disease. RT after BCS reduces the risk of in-breast recurrence, decreasing subsequent in-situ and invasive cancers by ≥50%, with 10-year breast-cancer specific survival outcomes approaching 98%. As local control rates are high, treatment efforts have focused on selective de-escalation of care. Traditionally, clinicians have used clinical-pathologic features (ie, grade, age, size, margin width) to guide selection of low-risk DCIS patients in whom postoperative RT may be omitted. More recently, genomic molecular assays including the Oncotype DX Breast DCIS Score and DCISionRT have been developed to provide individualized assessment of predicting RT benefit after BCS. These molecular assays have the potential for personalized risk assessment, particularly when used in combination with existing clinical-pathologic features for risk assessment. This article reviews the current status and existing published literature on DCIS molecular-risk assessment tools and their potential for guiding postoperative RT recommendations in the BCT setting. In addition, current trials studying omission of definitive surgery for low-risk DCIS are discussed.