Abstract RF2-01: Factors Influencing Additional Nodal Disease and Pathologic Nodal Upstaging with Axillary Dissection in Patients with Residual Node-Positive Breast Cancer After Neoadjuvant Chemotherapy Enrolled on Alliance A011202 Clinical Trial

Abstract

Abstract Background: The Alliance for Clinical Trials in Oncology A011202 randomized phase III trial enrolled patients (pts) with clinical T1-3 N1 breast cancer (BC) with residual node-positive disease on sentinel lymph node (SLN) surgery after treatment with neoadjuvant chemotherapy (NAC) to assess whether the recurrence-free interval with radiation to the undissected axilla and regional LNs (AxRT group) is non-inferior to axillary lymph node dissection (ALND) with RT (ALND group). Herein we report on the nodal burden in both groups of pts prior to randomization, and the percentage of pts who had additional positive nodes in the ALND group. Methods: The pathologic findings from surgery after completion of NAC of all eligible pts were summarized using descriptive statistics. A positive SLN was defined as metastasis ≥0.2 mm present in a node harvested at SLN surgery. Fisher’s exact test was used to assess whether the post-chemotherapy pathologic (ypN) category increased with the number of positive LNs found on ALND. Results: Of 1627 eligible pts registered on A011202, 785 (48.2%) were randomized to ALND and 842 (51.8%) to AxRT. Median age at study entry was 51 years (range: 19-87). Clinical T category prior to NAC was: cT1 in 18.7%, cT2 in 58.9% and cT3 in 22.4% of ALND; cT1 in 20.2%, cT2 in 56.5% and cT3 in 23.3% of AxRT group. Tumor subtype distribution was: 12.1% ER-/PR-/HER2-, 18.6% HER2+, 69.3% ER+ and/or PR+ HER2-. Disease was grade III in 41.5% of ALND group and 38.6% of AxRT group. The median number of LNs examined from SLN surgery was 4 (range: 1-8) for both ALND and AxRT arms. There were 99 pts (6.1%) who had 1 LN examined, 240 (14.8%) had 2 LNs examined, and 1288 (79.2%) had 3-8 LNs examined. Among the pts with 2-8 LNs examined from SLN surgery, 815 (53.3%; ALND: 53.7%; AxRT: 53.0%) had 1 positive SLN; 409 (26.8%; ALND: 26.6%; AxRT: 26.9%) had 2 positive SLNs; and 304 (19.9%; ALND: 19.7%; AxRT: 19.8%) had ≥3 positive SLNs. Nodal disease from SLN surgery was macroscopic in 83.6% (ALND: 84.9%; AxRT: 82.3%). In the ALND arm, 361 pts (46.0%) had additional positive nodes on ALND. This was significantly higher in pts with macrometastatic disease in the SLNs (47.5%) compared with those with micrometastatic disease in SLNs (37.1%) (p=0.043), but no significant differences were found between tumor subtypes (p=0.075). The percentage of pts with additional positive nodes on ALND increased as the number of positive nodes from SLN surgery increased: 33.3% with 1 positive SLN, 52.6% with 2 positive SLNs and 75.9% with ≥3 positive SLNs. The number of additional positive nodes on ALND was 1 for 130 (36.0%) pts, 2 for 70 (19.4%) pts, and ≥3 in 161 (44.6%) pts. ALND resulted in an increase in ypN category in 24.7% (194/785) of pts; 148 (18.8%) went from ypN1 to ypN2, 29 (3.7%) from ypN1 to ypN3, and 17 (2.2%) from ypN2 to ypN3. The increase in ypN category for the HER2+ BC [17.1% (25/146)] was significantly lower than that seen in the ER+ and/or PR+ HER2- BC [27.3% (150/549)] (p=0.013) and trended toward being lower than in ER- PR- HER2- BC (26.8% (19/71) (p=0.108). Conclusion: In patients with residual nodal positive disease after NAC, the rate of additional node-positive disease on completion ALND is high (46%) and increases with presence of SLN macrometastases and as the number of positive SLNs increases. ALND findings resulted in ypN category increase in 24.7% overall; this increase was less frequent in HER2+ disease. Additional data will be critical to understanding the value of ALND in the setting of positive SLNs after NAC in terms of impact on adjuvant treatment recommendations and outcomes. Support: U10CA180821, U10CA180882; U10CA180868 (NRG Oncology); U10CA180888 (SWOG); https://acknowledgments.alliancefound.org. Clinicaltrials.gov identifier: NCT01901094 Citation Format: Judy Boughey, Vera Suman, Kelly J. Hunt, Bruce G. Haffty, Thomas Buchholz, W. Fraser Symmans, Tracy L. Rieken, Travis J. Dockter, Jordan D. Campbell, Anna Weiss, Julie A. Bradley, Joshua M. V. Mammen, Ann H. Partridge, Lisa A. Carey. Factors Influencing Additional Nodal Disease and Pathologic Nodal Upstaging with Axillary Dissection in Patients with Residual Node-Positive Breast Cancer After Neoadjuvant Chemotherapy Enrolled on Alliance A011202 Clinical Trial [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr RF2-01.

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