324P - Nodal underestimation rate in early-stage ER+/HER2- breast cancer patients with limited positive sentinel lymph nodes in the era of precise medicine: A real-world multicenter analysis from 40 institutions in China

Background

Emerging data show more estrogen receptor-positive/ human epidermal growth factor receptor 2-negative (ER+/HER2-) early breast cancer patients with 1-3 positive sentinel lymph nodes (SLNs) omitted axillary lymph node dissection (ALND) but received adjuvant radiation therapy, which led to equivalent locoregional and distant disease control. In this study, we aimed to evaluate whether sentinel lymph node biopsy (SLNB) only can provide accurate lymph node staging to select candidates for multigene assay testing and adjuvant CDK4/6 inhibitor treatment in ER+/HER2- breast cancer patients with 1-3 positive SLNs.

Methods

Consecutive patients with cT1-3N0, ER+/HER2- disease, and 1-3 positive SLNs were retrospectively included from the multicenter Shanghai Jiao Tong University-Breast Cancer Database. The nodal underestimation rate (NUR) was calculated in patients receiving SLNB+ALND in the overall population and in potential candidates for multigene assays and CDK4/6 inhibitors according to the RxPONDER, MINDACT, and monarchE trials.

Results

Among the 3672 patients included, 24.1% received SLNB only. The overall NUR was 9.5%. For those who met the inclusion criteria for the RxPONDER, MINDACT, and monarchE trials, positive non-SLNs were found in 3.0%, 3.5%, and 3.7% of the patients, respectively. The low NUR was not influenced by breast surgery modality. Additional ALND upon SLNB brought no survival benefit for eligible patients of these trials (RFI P=0.090; OS P=0.772).

Conclusions

ALND can be safely omitted in cT1-3N0, ER+/HER2- breast cancer patients with 1-3 positive SLNs when selecting candidates for multigene assays testing and adjuvant CDK4/6 inhibitor treatment.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.