Factors Influencing Suboptimal Pathologic Margins and Re-Excision Following Breast Conserving Surgery for Ductal Carcinoma In-Situ

Introduction: Re-excisions following breast conserving surgery (BCS) are common, occurring more frequently in ductal carcinoma in-situ (DCIS) than its' malignant counterpart. Although one quarter of patients with breast cancer will have DCIS, there is limited information available regarding factors predisposing to inadequate pathologic margins, and the need for re-excision. Methods: Retrospective review of patients treated for DCIS between the years 2010-2016 was conducted. Patients with DCIS undergoing BCS were identified and evaluated for demographic and pathologic factors associated with suboptimal pathologic margins and re-excision. Multivariate analysis with Wald Chi-Square testing was performed. Results: 241 patients underwent BCS with suboptimal margins (SOM) in 51.7% (123/238), with 27.8% undergoing re-excision (67/241). Tumor size was the most influential variable, positively associated with SOM (OR = 10.25, CI: 5.50-19.13) and re-excision (OR = 6.36, CI: 3.92-10.31). Patient age was inversely associated with SOM (OR = 0.58, CI: 0.39-0.85) and subsequent re-excisions (OR = 0.56, CI: 0.36-0.86). Low tumour grade was associated with re-excision (OR = 1.31, CI: 0.63-2.71), while ER negative disease was associated with SOM (OR = 2.24, CI: 1.21-4.14). Discussion: Inadequate pathologic margins following BCS, and subsequent re-excision rates are common in patients with DCIS, and consistent with the literature. Tumour size is the dominant factor driving this occurrence, with patient age and tumour grade also impacting outcomes.