The association between age and lymph node status among patients with breast cancer after neoadjuvant chemotherapy: Eastern European population-based retrospective cohort study

It is estimated that the incidence of breast cancer (BC) will steadily increase, particularly within the elderly (≥ 65 years of age) group of patients. In this population, both breast-conserving treatment (BCT) and mastectomy have been proven effective in terms of overall survival (OS). However, the debate over the necessity of axillary procedures (sentinel node biopsy, axillary lymph node dissection) among elderly BC individuals remains ongoing. With limited data on clinical outcomes among elderly BC patients receiving neoadjuvant chemotherapy (NAC) in Eastern European individuals, the aim of the current study was to evaluate the association between age and LN status on clinical outcomes and OS in BC patients after NAC. In addition, the influence of demographic and clinical factors on the incidence of LN metastasis was assessed. Female patients with histologically confirmed non-metastatic (cT1-4N0-3M0) BC who underwent multimodal treatment and with curative intent between 2013 and 2023 in two Polish university centers were included in the study and divided into elderly (≥ 65) and non-elderly (< 65) groups. Patients who had not undergone NAC or had incomplete histopathological report or survival data were excluded. A total of 637 patients were included in the final analytic cohort. In both the elderly (n = 136) and non-elderly (n = 501) groups, higher clinical tumor (cT) stage, higher post treatment pathological tumor (ypT) stage, and clinically positive nodes (cN+) were associated with increased odds of postoperative metastatic LNs (all p < 0.01). Residual nodal disease (ypN+) and higher ypT stage were associated with worse OS in the non-elderly group, (HR = 5.95; 95% CI 2.38–14.90; p = 0.0002; and HR = 1.99; 95% CI 1.09–3.63; p = 0.0259, respectively). In contrast, in the elderly group, ypN status was not significantly associated with OS. In this Eastern European cohort of BC patients treated with NAC, post-treatment lymph node status showed age-dependent prognostic value. Residual nodal disease remained a strong adverse prognostic factor in non-elderly patients, whereas its association with overall survival was not observed in elderly patients. These findings support further research on age-tailored axillary strategies after NAC, ideally in prospective studies.