Background: There are few established indications for sentinel lymph node biopsy (SLNB) in breast ductal carcinoma in situ (DCIS). This study examines factors contributing to the high rate of SLNB in DCIS in Alberta, Canada.
Methods: Patients who underwent definitive surgery from January 2009 to July 2011 for DCIS diagnosed on preoperative core-needle biopsy were identified using a provincial synoptic operative report database (WebSMR). The relationship between baseline patient and tumor characteristics and treatment with total mastectomy (TM), use of SLNB, and upstaging were examined.
Results: There were 394 patients identified in the study cohort. Mean age was 57 years, and average preoperative tumor size was 3 cm. Overall, 148 patients (37.6 %) underwent TM; predictors were preoperative tumor size [odds ratio (OR), 1.92 per 1-cm increase in size; 95 % CI 1.65-2.24] and surgeon. Upstaging to invasive cancer at surgery occurred in 23 %, predicted only by preoperative tumor size (OR 1.14 per 1 cm; 95 % CI 1.03-1.27). SLNB was performed in 306 patients overall (77 %) and 140 of those treated with BCS (61 %). Predictors of SLNB were larger preoperative tumor size (OR 1.55 per 1 cm; 95 % CI 1.18-2.04) and the surgeon. In patients treated with BCS, 3 patients who were upstaged had positive SLNs (>0.2 mm), and no patients with DCIS had a positive SLN.
Conclusions: SLNB use is high in patients undergoing BCS for DCIS. Tumor size and the operating surgeon predicted SLNB use. Despite a 23 % upstaging rate, the rate of clinically significant positive SLNs in patients treated with BCS is low, supporting omission of upfront SLNB.