Abstract PO5-06-03: Impact of curative-intent treatment on survival for metastatic breast cancer limited to distant lymph nodes
Authors: Xu Yang 
Published: May 2024

Abstract
BACKGROUND:
Metastatic breast cancer limited to distant lymph nodes is classified as stage IV but potentially represents an anatomically distinct entity amenable to curative treatment. Its optimal management is unclear, with existing studies limited by small sample sizes and short follow-up durations. We sought to investigate the impact of curative-intent treatment on breast cancer-specific survival (BCSS) and overall survival (OS) for patients with this diagnosis.
METHODS:
Three cohorts of patients diagnosed with breast cancer from 2010 to 2019 were identified from the Surveillance, Epidemiology, and End Results 17 registries database. The curative cohort consisted of patients with metastatic breast cancer involving only distant lymph nodes who received a combination of chemotherapy, surgery to the primary site, and radiotherapy (curative-intent treatment). The palliative cohort included patients who underwent chemotherapy but not curative-intent treatment. The N3c cohort was comprised of patients with ipsilateral supraclavicular lymph node metastases but no distant metastases who received curative-intent treatment. Weighting based on covariate balancing propensity scores was performed to balance age, sex, race, median household income, year of diagnosis, T stage, histology, pathological grade, and ER/PR/HER2 status between the cohorts. Weight-adjusted multivariable Cox regression models with the same covariates were then used to compare the BCSS and OS of the three cohorts.
RESULTS:
A total of 2,089 patients with a median follow-up of 37 months were eligible for analysis, of whom 577 (27.6%) were in the curative cohort, 905 (43.3%) were in the palliative cohort, and 607 (29.1%) were in the N3c cohort. After propensity score weighting, the maximal standardized mean difference for all covariates was less than 0.1. Five-year BCSS for patients in the weight-adjusted curative, palliative, and N3c cohorts were 63.0% (95% CI 58.1-68.3), 46.7% (42.4-51.4), and 66.4% (61.4-71.8), respectively; and five-year OS were 57.9% (53.0-63.2), 41.2% (37.2-45.7), and 62.2% (57.3-67.6), respectively. Compared to the palliative cohort, the curative cohort exhibited better BCSS (HR 0.47, 95% CI 0.38-0.57; P&lt; 0.001) and OS (HR 0.48, 95% CI 0.40-0.58; P&lt; 0.001). In contrast, the N3c cohort had similar BCSS (HR 0.93, 95% CI 0.73-1.17; P=0.53) and OS (HR 0.96, 95% CI 0.77-1.19; P=0.68) to the curative cohort.
CONCLUSIONS:
Patients treated curatively for metastatic breast cancer limited to distant lymph nodes had higher BCSS and OS than those receiving palliative chemotherapy and similar BCSS and OS to patients receiving curative-intent treatment for ipsilateral supraclavicular lymph node metastases. These results support the use of aggressive multimodal therapy for select stage IV breast cancer patients with only distant nodal metastases and, if confirmed, suggest that a substantial portion of such patients may be undertreated.
Citation Format: Yang Xu. Impact of curative-intent treatment on survival for metastatic breast cancer limited to distant lymph nodes [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO5-06-03.