Significance of Axillary Lymph Node Metastasis in Primary Breast Cancer

Abstract

PURPOSE: Axillary lymph node status is the single most important prognostic variable in the management of patients with primary breast cancer. Yet, it is not known whether metastasis to the axillary nodes is simply a time-dependent variable or also a marker for a more aggressive tumor phenotype. The purpose of this study was to determine whether nodal status at initial diagnosis predicts outcome after relapse and therefore also serves as a marker of breast cancer phenotype. PATIENTS AND METHODS: Survival experience after first relapse in 1,696 primary breast cancer cases was analyzed using Cox proportional hazards regression. The following explanatory variables and their first-order interactions were considered: number of axillary lymph nodes involved (zero v one to three v four or more), hormone receptor status (any estrogen receptor [ER] negativity v ER negativity/progesterone receptor positivity v other ER positivity), primary tumor size (< 2 cm v 2 to 5 cm v > 5 cm), site of relapse (locoregional v distant), disease-free interval (< 1.5 years v 1.5 to 3 years v > 3 years), adjuvant endocrine therapy (none v any), adjuvant chemotherapy (none v any), and menopausal status (pre-, peri-, or postmenopausal). RESULTS: Axillary lymph node status, site of relapse, and hormone receptor status were all highly significant as main effects in the model. After adjustment for other variables, disease-free interval alone was only modestly significant but interacted with nodal status. After disease-free interval, hormone receptor status, and site of relapse were accounted for, survival after relapse was poorer in node-positive cases, when compared with node-negative cases. The hazard ratios for patients with one to three and four or more involved nodes were 1.2 (95% confidence interval [CI], 0.8 to 1.9) and 2.5 (95% CI, 1.8 to 3.4), respectively. CONCLUSION: Patients with four or more involved nodes at initial diagnosis have a significantly worse outcome after relapse than node-negative cases, regardless of the duration of the disease-free interval. We conclude that nodal metastasis is not only a marker of diagnosis at a later point in the natural history of breast cancer but also a marker of an aggressive phenotype.