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Ductal carcinoma in-situ (DCIS) of the breast has rapidly increased in incidence over the past several decades secondary to an increased use of screening mammography. Local treatment options for women diagnosed with DCIS include mastectomy or breast-conserving therapy (BCT). While several randomized trials have confirmed a greater than 50% reduction in the risk of local recurrence with the administration of radiation therapy (RT) compared to breast-conserving surgery (BCS) alone, controversy persists regarding whether or not RT is needed in selected ‘low-risk’ patients. Over the past two decades, two prospective single-arm studies and one randomized trial have been performed and confirm that the omission of RT after surgery alone is associated with higher rates of local recurrence even after selecting patients with the most optimal clinical and pathologic features. Importantly, these trials have failed to consistently and reproducibly identify a low-risk cohort of patients (based on clinical and pathologic features) that does not benefit from RT. As a result, adjuvant RT is still advocated in the majority of patients, even in these low-risk cases. Future research is moving beyond traditional clinical and pathologic risk factors and instead employing more modern approaches such as multi-gene assays and biomarkers with the hopes of identifying truly low-risk patients who may not require RT. However, recent studies confirm that even low-risk patients identified from multi-gene assays have higher rates of local recurrence with local excision alone than would be expected with the addition of radiation therapy.