P2: Incidence of lymph node involvement in clinically node-negative breast cancer patients following neoadjuvant chemotherapy and identification of clinicopathologic features which may lead to omission of sentinel lymph node biopsy

Introduction: Neoadjuvant chemotherapy (NAC) is now being utilized for earlier stage breast cancer. While removing axillary lymph nodes (LN) has long played a role in guiding treatment, its role in clinically node-negative patients undergoing NAC has yet to be elucidated. The goal of this study was to evaluate the incidence of residual occult pathologic nodal disease after NAC in this patient population and to identify associated clinicopathologic risk factors.


Methods: We conducted a retrospective study of women who received NAC at our institution from January 2010 to December 2021 (n = 657). We defined LN- status prior to NAC based on axillary ultrasound. We excluded LN+ patients prior to NAC, neoadjuvant hormonal therapy, and inflammatory breast cancer. Clinical and pathologic tumor features were compared between two groups: persistent LN- vs LN+ after NAC.


Results: We identified 297 patients who received neoadjuvant systemic therapy for LN- breast cancer, of whom 166 patients who received NAC defined the study group. Nineteen patients (11.4%) had pathologic positive LNs following NAC. In comparing the two cohorts, patients that were LN+ (n = 19) compared to LN- (n = 147) after NAC tended to have clinically larger mean tumor size (4.5 cm vs. 3.2 cm, p < 0.01), higher clinical T stage (T1 5%, T2 53%, T3 31%, and T4 11%, vs T1 19%, T2 70%, T3 10%, and T4 1%, p < 0.001), invasive lobular cancer (21% vs 7%, p < 0.01), lymphovascular invasion (40% vs 11%, p < 0.01), and ER+, HER2- phenotype (63% vs 22%, p < 0.01). In contrast, LN- patients after NAC were more likely to have HER2+ tumors (40% vs 5%, p < 0.01) and pathologic complete response in the breast (24% vs 5%, p = 0.05). There was no significant difference between the two cohorts in incidence of triple negative breast cancers, mean patient age, menopausal status, the presence of multifocal/multicentric tumors, and tumor grade. Finally, among patients who remained LN- after NAC, a mean of 3.8 sentinel LNs were harvested with 59 patients (41%) having >3 sentinel LNs removed.


Conclusions: The present study found a low incidence of residual occult pathologic nodal disease in clinically node-negative patients undergoing NAC. Furthermore, a significant number of LNs were found to be harvested in this low-yield population that may lead to unnecessary morbidity and cost without clinical utility. This is the first study to characterize clinical and pathologic features that may identify clinically node-negative patients following NAC who may avoid SLNB.