E21: Axillary Lymph Node Dissection Should Not Be Avoided in Patients Who Undergo Neoadjuvant Chemotherapy for a Positive Sentinel Node after Targeted Axillary Staging

Introduction: Recent studies have demonstrated the utility and reliability of sentinel lymph node biopsy (SLNB) or targeted axillary dissection with sentinel node biopsy (TAD) in predicting residual tumor burden in node positive breast cancer (BC) patients who undergo neoadjuvant chemotherapy (NAC). De-escalation of axillary surgery with omission of axillary lymph node dissection (ALND) in patient with a negative SLN after TAD or SLNB following NAC for node positive BC is becoming increasingly accepted.  The aim of our study was to compare residual axillary disease burden, adjuvant treatment and recurrence after TAD vs SLNB in patients with node positive disease after NAC. 

Methods:

Methods: Patients undergoing NAC for stage II-III node positive BC from 02/2016 – 6/2022 were identified from a prospectively maintained database. Patients who were clinically node negative (cN0) after NAC, had a positive SLN after either TAD or SLNB alone and underwent ALND were evaluated.

Results:

Results: Of the 471 patients who underwent NAC, 157 (33%) had stage II-III node-positive BC and were cN0 after NAC and prior to surgery.  66 (42%) patients had no TAD or SLNB due to positive nodes. 39 (25%) patients had an ALND after TAD or SLNB, of which 23 (59%) had TAD and 16 (41%) had SLNB alone (Table). There were no significant differences between the SLNB vs TAD groups including median age (47 vs 47 years; P=0.94) tumor size (2.9 vs 3.4cm p=0.646), or receptor status with a majority of tumors being ER+/HER2-neg (73.9 vs 81.3% p=0.50).  More patients underwent mastectomy in the TAD group (82.6% vs 17.4%).  Patients in the TAD group had a significantly higher median number of SLN excised compared to SLNB alone (SLNB 3 nodes, TAD 5 nodes, p=0.017), although no differences in the number of positive SLN (2.43 vs 2.06, p=0.48) were observed.   There were significant differences between the groups in additional number of positive nodes after ALND (SLNB: 2.9 [0-8] vs TAD: 1.9 [0-13], p= 0.017. All patients received adjuvant chest wall radiation (RT), 23 (59%) received nodal RT, and 6 (15%) received supraclavicular/internal mammary nodal RT.  There was one (2.6%) axillary recurrence and 3 (7.7%) distant recurrences at median follow-up of 38 (12-65) months.

Conclusions:

Conclusions: Completion axillary dissection may identify significant residual nodal disease in patients who undergo NAC for node positive breast cancer and are found to have a positive sentinel node after either TAD or SLNB.  Information gained from ALND can guide extent of adjuvant treatment and may alter radiation fields.