Predictive factors of isolated tumor cells and micrometastases in axillary lymph nodes in breast cancer

Abstract

Introduction: Since the introduction of the sentinel lymph node biopsy (SLNB) in patients with breast cancer, micrometastases and isolated tumor cells are detected frequently in the SLN. As such, they offer an opportunity to study the development of regional metastases in breast cancer.

Patients and methods: Between June 1999 and November 2010 1418 patients with cT1-2N0 breast cancer underwent SLNB. Primary tumor characteristics and information regarding regional lymph node involvement were collected prospectively. Patients were categorized into four levels of lymph node involvement: pN0, pN0(i+), pN1mi and pN ≥ 1a. An univariate analysis and a binary logistic regression analysis were performed to assess the relation between patient- and tumor characteristics and lymph node involvement.

Results: Increasing tumor size and younger age were associated with a higher risk of pN1mi and pN ≥ 1a and a lower chance of pN0 and pN0(i+). Triple negative molecular subtype was associated with a decreased risk of pN1mi and pN ≥ 1a. Tumor size was positively related to overall occurrence of regional lymph node metastases in a linear manner.

Conclusion: Patients with larger tumors, no triple negative disease, and younger age showed a decreased chance of both pN0 and pN0(i+) and an increased risk of both pN1mi and pN ≥ 1a. There seems to be a gradual shift in risk pattern from pN0 to pN0(i+) to pN1mi and to pN ≥ 1a-disease. The presence of the smallest metastases remained fairly constant over time when compared to macrometastases. This constant presence suggests that the risk of seeding and outgrowth of metastases remains constant over time.

Keywords: Breast cancer; Isolated tumor cells; Lymph node metastases; Micrometastases; Predictive factors; Tumor characteristics.