BackgroundCurrent guidelines do not recommend routine sentinel node biopsy (SLNB) for ductal carcinoma in situ (DCIS), except in the setting of mastectomy or microinvasive disease. This study aimed to evaluate national SLNB utilization in women undergoing upfront mastectomy for DCIS, identify predictors of SLNB utilization, and determine the percentage with a positive SLNB. MethodsA retrospective cohort analysis was performed using the NCDB of women with clinical DCIS who underwent upfront mastectomy between 2012–2017. Demographic and clinicopathologic variables were compared between patients who underwent SLNB and those who did not. Multivariate logistic regression models were used to identify factors associated with SLNB utilization and positive SLNB. Results38,973 patients met inclusion criteria: 34,231 (88%) underwent SLNB and 4,742 (12%) had no surgical axillary staging. Most patients were age 50–69 (51%), non-Hispanic White (71%), with private insurance (66%). On multivariate analysis, older patients were less likely to receive SLNB (p<0.01), while patients with higher grade DCIS were more likely to undergo SLNB (p<0.01). In those who underwent SLNB (n=34,231), only 1,149 (3.4%) had nodal involvement. Non-Hispanic Black patients had increased odds of a positive SLNB (p<0.01), while those with estrogen receptor positive disease were less likely to be node positive (OR 0.68, p<0.001). ConclusionsWhile 88% of patients had a SLNB, only 3.4% were found to be node positive. Given this low rate, it is reasonable to consider SLNB omission in select patients with low grade, hormone receptor positive DCIS undergoing upfront mastectomy. Micro AbstractThe NCDB was used to examine SLNB utilization in patients with DCIS undergoing upfront mastectomy. Findings indicated low rates of nodal involvement and that hormone receptor-negative and high-grade DCIS were associated with positive SLNB, suggesting it is reasonable to consider SLNB omission for select populations.