Does 8-guage stereotactic core needle biopsy improve the accuracy over 11-gauge devices? Evaluation of pure DCIS on stereotactic biopsy and the rate of upstaging.

97 Background: Ductal carcinoma in situ (DCIS) accounts for 25% of newly diagnosed breast cancers. Core needle biopsy (CNB) has replaced open surgical biopsy for mammographic calcifications. We compare our experience with 8-gauge vs. 11-gauge vacuum assisted core needle biopsy in pure DCIS. We hypothesize that the diagnosis of DCIS with use of an 8-gauge vacuum-assisted core needle will lead to a lower rate of upstaging to invasive cancer at definitive surgical excision compared to 11-gauge vacuum-assisted core needle biopsy. Methods: A retrospective study was performed evaluating all patients who underwent a stereotactic core needle biopsy at our institution for DCIS during 2008-2012.We then compared the upstaging rates between patients biopsied using 8 or 11-gauge biopsy devices. Results: A total of 580 patients underwent STCNB during 2008-2012 at our institution, there were 461 patients excluded as they did not meet inclusion criteria and 119 patients were included. The most common mammographic finding was calcifications in 104/119 (87.4%) and a mammographic mass in 15/119 (12.60%). Biopsy with the 11 gauge needle was utilized in 60 patients and 59 patients with 8-G needle. Factors associated with upstaging were using a smaller 11 gauge needle and a mass on imaging, higher grade and more than four cores obtained on biopsy. There was an upstaging rate of 17/60 (28%) in patients who underwent stereotactic biopsy using a11-gauge needle versus upstaging rate of 7/59 (11.8%) in patients who underwent stereotactic biopsy using 8 gauge needle. We obtained a statistically significant p-value of 0.025. Conclusions: This is one of the few studies comparing upstaging rates from pure DCIS on STCNB using 8 and 11-gauge stereotactic vacuum assisted needles. Our results show that there is a statistically significant decrease in upstaging of pure DCIS to invasive malignancy at excision using the larger 8-gauge needle devices. The clinical implication is that SLNB need not be performed secondary to the low upstaging rate. We recommend that all stereotactic core needle biopsies be performed using the 8-gauge needle devices, and that SLNB generally be omitted for DCIS.