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Breast

E24: Significance of Residual Nodal Disease in Clinically Node-Negative Breast Cancer after Neoadjuvant Chemotherapy

Introduction: ACOSOG Z0011, IBCSG 23-01 and AMAROS showed axillary lymph node dissection (ALND) may be omitted in early stage cN0 breast cancer treated with upfront surgery and low-volume sentinel lymph node (SLN) metastasis. Patients receiving neoadjuvant chemotherapy (NCT) were excluded and although less likely to have positive SLNs, ALND is recommended. We evaluated factors associated with a positive SLN (+SLN) and positive non-SLNs (+non-SLNs) on ALND in cN0 breast cancer after NCT.

Methods: A prospective database was queried for patients with cT1-2N0M0 breast cancer treated with NCT and SLN biopsy with or without ALND from 1996-2022. Exam and nodal ultrasound determined cN0 status. Demographics, tumor and treatment factors were evaluated. Logistic regression models identified factors predictive of positive SLNs and +non-SLNs on ALND.

Results: Of 1930 patients, 1696 (87.9%) had negative SLNs and 234 (12.1%) had a +SLN. The median number of SLNs excised was 2 (p=0.2). A +SLN was associated with cT2 category, initial tumor size, hormone receptor (HR)-positive/HER2-negative status (HR+HER2-), grade 1, multifocal disease, and lobular histology. HR+HER2-status (OR 2.5; p < 0.0001), lobular histology (OR 1.8; p=0.01), and cT2 category (OR 1.6; p=0.02) predicted a +SLN. Of patients with a +SLN and known SLN met size (n=234), 148 (63.2%) received ALND. Of these, 109 (73.6%) had no additional disease and 39 (26.4%) had +non-SLNs on ALND. By SLN met size, no +non-SLNs were identified in patients with isolated tumor cells (ITC) whereas 12.3% with micromets and 37.6% with macromets had additional +non-SLNs (p=0.01). More patients with macromets underwent ALND compared to ITCs or micromets (p< 0.001) (Table 1). Positive non-SLNs on ALND correlated with older age, HR+HER2- status, and higher number of SLNs. At 5-year median follow-up, in patients with +SLNs, 7 (3%) had local, 3 (1.3%) regional, and 29 (12.4%) distant recurrences, and 24 (10.3%) died. Of those with regional recurrence, 2 had ALND without additional positive nodes and 1 had SLN biopsy alone.

Conclusions: In early stage cN0 breast cancer treated with NCT, HR+HER2- status, lobular histology, and cT2 category predict positive SLNs. SLN met size correlates with additional disease on ALND as those with SLN-ITC had no +non-SLNs compared to SLN-micromets and macromets. Patients with p</span>ositive SLNs had low locoregional recurrence rates. These findings suggest further investigations exploring omission of ALND in patients with low volume SLN disease after NCT is warranted.

Learning Objectives:

  • Upon completion, participant will be able to identify factors associated with positive sentinel lymph node biopsies in patients with cN0 breast cancer treated with neoadjuvant chemotherapy.
  • Upon completion, participant will be able to identify factors associated with residual disease on axillary lymph node dissection in patients with cN0 breast cancer treated with neoadjuvant chemotherapy.
  • Upon completion, participant will be able to identify local and regional recurrence rate in patients with cN0 breast cancer treated with neoadjuvant chemotherapy.