Prognostic Value of Lymph Node Micrometastases in Breast Cancer: A Multicenter Cohort Study

BACKGROUND: To evaluate the prognostic meaning of lymph node micrometastases in breast cancer patients. METHODS: Between January 2000 and January 2003, 1411 patients with a cT(1-2)N(0) invasive breast carcinoma underwent surgery in 7 hospitals in the Netherlands. Sentinel lymph node biopsy was done in all patients. Based on lymph node status, patients were divided into 4 groups: (p)N(0) (n = 922), (p)N(1micro) (n = 103), (p)N(1a) (n = 285), and (p)N(≥1b) (n = 101). Median follow-up was 6.4 years. RESULTS: At the end of follow-up, 1121 women were still alive (79.4%), 184 had died (13.0%), and 106 were lost to follow-up (7.5%). Breast cancer recurred in 244 patients: distant metastasis (n = 165), locoregional relapse (n = 83), and contralateral breast cancer (n = 44). Following adjustment for possible confounding characteristics and for adjuvant systemic treatment, overall survival (OS) remained comparable for (p)N(0) and (p)N(1micro) and was significantly worse for (p)N(1a) and (p)N(≥1b) (hazard ratio [HR] 1.18; 95% confidence interval [95% CI] 0.58–2.39, HR 2.47; 95% CI 1.69–3.63, HR 4.36; 95% CI 2.70–7.04, respectively). Disease-free survival (DFS) was similar too in the (p)N(0) and (p)N(1micro) group, and worse for (p)N(1a) and (p)N(≥1b) (HR 0.96; 95% CI 0.56–1.67 vs HR 1.64; 95% CI 1.19–2.27, HR 2.95; CI 1.98–4.42). The distant metastases rate also did not differ significantly between the (p)N(0) and (p)N(1micro) group and was worse for (p)N(1a) and (p)N(≥1b) (HR 1.22; 95% CI 0.60–2.49, HR 2.26; 95% CI 1.49–3.40, HR 3.49; CI 2.12–5.77). CONCLUSIONS: In breast cancer patients survival is not affected by the presence of micrometastatic lymph node involvement. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1245/s10434-010-1451-z) contains supplementary material, which is available to authorized users.