Comparison of Clinicopathological Features and Survival Between Distant Lymph Node Metastasis and Distant Micrometastasis in Breast Cancer.

BACKGROUND

The clinical value of distant lymph node (DLN) metastasis for breast cancer prognosis still lacks consensus, and scholars dispute whether it should be categorized as M1 stage disease. Similarly, distant micrometastasis [M0(i+)] has been associated with adverse outcomes despite being staged as M0. This study compared the clinicopathological characteristics and survival outcomes of DLN metastasis and M0(i+) breast cancer to clarify the prognostic significance of DLN metastasis.

METHOD: We extracted data of female breast cancer cases diagnosed during 2018 to 2022 from the SEER database. Cases with isolated DLN metastasis or M0(i+) were enrolled. Baseline indicators were compared using chi-square test and t-test. After 1:1 propensity score matching, survival differences were analyzed. Kaplan-Meier curves and Cox models were used for OS analysis, while cumulative incidence functions and Fine-Gray models were applied to assess BCSM.

RESULT: Among 345,138 original cases, 1,315 patients were finally enrolled (DLN: n = 731; M0(i+): n = 584). DLN metastasis was linked to larger tumors, higher histologic grade, more ER/PR negativity, more HER2 positivity, increased triple-negative subtype, and higher T/N stage (all P < .001). Following matching, patients with DLN metastasis presented notably inferior OS and BCSM compared with those with M0(i+) status (all P < .001). Multivariate regression verified that DLN metastasis was an independent risk factor for poor prognosis, with HR of 3.82 (CI: 2.20-6.64) for OS and 3.76 (95% CI, 2.06-6.85) for BCSM.

CONCLUSION

DLN metastasis indicates more aggressive tumor characteristics and inferior prognosis relative to M0(i+). These findings provide evidence supporting the consideration of DLN metastasis as M1 stage disease.