The Importance of Applying ACOSOG Z0011 Criteria in the Axillary Management of Invasive Lobular Carcinoma: A Multi-institutional Cohort Study

Background. The American College of Surgeons Oncology Group (ACOSOG) Z0011 trial led to a significant change in the management of patients with early stage breast cancer and limited sentinel lymph node (SLN) metastases. However, only 27 patients with invasive lobular carcinoma (ILC) were randomized to the completion axillary lymph node dissection (ALND) arm. To assess the generalizability of the Z0011 trial, the primary aim of this study was to determine the risk of residual nodal burden (RNB) for ILC. Methods. A multi-institutional cohort study was completed. RNB was determined for women of any age with an ILC and at least one positive SLN who underwent a primary breast procedure (lumpectomy or mastectomy) and both a SLN biopsy followed by a completion ALND between July 1, 1999, and June 30, 2009, at two large academic centers. Results. A total of 59 patients (60 ILCs) met the inclusion criteria. Although the overall RNB was 40 %, it was significantly greater in the T3+ group compared to T1/T2 (87 vs. 24 %, respectively, p < 0.0001). When comparing only ILCs that met all of the inclusion criteria for ACOSOG Z0011 (T1 or T2, 1 or 2 SLNs positive, no SLN extranodal extension, and breast conservation) to those ILCs that did not, the RNB was significantly greater in the latter (56 vs. 17 %; p < 0.003). Conclusions. Overall, the clinical practice changes that have occurred after publication of the ACOSOG Z0011 trial appear to be generalizable to ILCs within the inclusion criteria of the study.