Perez, E.

612 Background: The adoption of new breast surgical techniques has been rapid for early stage breast cancer. The utilization of these techniques in patients with high risk operable breast cancer has not been thoroughly investigated. Methods: Retrospective surgical data was summarized for patients entered into N9831 “Phase III Trial of Doxorubicin and Cyclophosphamide Followed by Weekly Paclitaxel With or Without Trastuzumab as Adjuvant Treatment for Women With HER-2 Over-expressing or Amplified Node Positive or High-Risk Node Negative Breast Cancer.” Results: 3,505 patients were entered into N9831 from 2000–2005 following primary surgery for breast cancer. The median age was 50 and 43% were premenopausal. 93% of patients underwent a diagnostic biopsy prior to their definitive surgical procedure. Whether HER2-neu status was available at time of definitive surgery is unknown. 61% underwent a mastectomy whereas 39% underwent breast conserving surgery (BCS). The rate of BCS was relative stable over the course of the trial. Patients with T1 tumors had a higher rate of BCS (49%) compared to T2 tumors (37%) and T3 tumors (6%). Sentinel lymph node (SLN) biopsy was performed in 54% of the cases. The rate of SLN biopsy increased from 40% in 2000 to 66% in 2005. Patients who underwent mastectomy had a lower rate of SLN biopsy than patients who underwent BCS (44% versus 71%, respectively). Tumor size was also associated with the rate of SLN biopsy: T1 (60%), T2 (53%), and T3 (36%). Data on local and regional recurrences are still maturing. Conclusions: Surprisingly, low numbers of patients on this trial underwent BCS whereas the adoption of the SLN biopsy procedure among the same group of surgeons was relatively high. The relatively low rate of BCS in this study population needs further investigation to determine what surgeon and patient factors impacted the surgical decision. No significant financial relationships to disclose.