Abstract CS1-2: Optimal management of the axilla: A look at the evidence

The surgical management of the axilla has undergone significant evolution during the past 20 years. The inception of the sentinel lymph node (SLN) concept and the clinical validation of lymphatic mapping and SLN biopsy (SLNB) starting in the 1990s, challenged the century-old primacy of axillary lymph node dissection (ALND) as the procedure of choice for staging the axilla and ushered us into a new era of axillary surgical management. Randomized clinical trials, evaluating SLNB with or without completion ALND in patients with operable breast cancer and negative SLN(s), established SLNB alone as the standard of care for staging the axilla in this setting. These trials established the performance characteristics of SLNB and factors that affect identification and false-negative rate and led to the refinement of the original SLN node concept. More importantly, the results from these trials provided the launching pad for the conduct of additional randomized trials evaluating SLNB alone vs. SLNB with completion ALND in patients with operable breast cancer and limited SLN involvement (micrometastases in IBCSG 23-01 or macrometastases in 1 or 2 SLNs in ACOSOG Z0011). These trials demonstrated no disease-free or overall survival advantage with completion ALND, thus expanding the use of SLNB alone in patients with limited SLN involvement. Another clinical trial (AMAROS) compared the effect of axillary radiotherapy vs. completion ALND in patients with positive SLN(s) and demonstrated equivalent oncologic outcomes between the two approaches but with less morbidity in favor of axillary radiotherapy. Thus, for patients who meet the criteria for inclusion in the ACOSOG Z11 and the IBCSG 23-01 trials, SLNB alone without completion ALND is adequate for staging the axilla. For patients who meet the criteria for inclusion in the AMAROS trial, axillary radiotherapy appears to represent a better option than completion ALND. Lastly, the increasing use of neoadjuvant chemotherapy in appropriately-selected patients with large operable breast cancer and the resulting axillary nodal down-staging in a considerable proportion of patients with axillary lymph node involvement at presentation, has led to an increased interest in the evaluation of SLNB in this setting. After a decade-old debate, the prevailing approach for patients who present with clinically negative axilla and are considered for neoadjuvant chemotherapy, is to perform SLNB after neoadjuvant chemotherapy. This approach has now also been expanded to include patients who present with clinically (or biopsy proven) involvement of the axillary nodes, become clinically node-negative after neoadjuvant chemotherapy and have negative SLNB. Several prospective trials (ACOSOG Z1071, SENTINA, SN FNAC) have recently demonstrated the feasibility and accuracy of SLNB alone in this setting. Provided that certain procedures are followed (removal of 3 or more SLNs, dual-agent lymphatic mapping, localization and removal of previously biopsied positive nodes and even the use of immunohistochemistry in the SLN evaluation), the false-negative rate of SLNB drops to below 10%. Adoption of this approach has the potential to further decrease the use of ALND in patients who present with documented axillary lymph node involvement. Citation Format: Mamounas EP. Optimal management of the axilla: A look at the evidence. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr CS1-2.