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Triple-negative breast cancer and likelihood of nodal metastates.
General Session IV: Poster Discussion A
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: Axillary lymph node metastases are a prognostic indicator for breast cancer. Studies suggest that breast cancer subtypes are associated with the presence of lymph node (LN) metastases. The purpose of this study was to determine if patients with triple negative breast cancer (TNBC) have a higher risk of LN metastases than those with non-TNBC. Methods: Prospective database review identified 2,967 female patients with invasive breast cancer treated with mastectomy or breast conserving surgery (BCS) between January 2000 and May 2012. Only patients who underwent sentinel node biopsy (SNB) and/or axillary lymph node dissection (ALND) were included. Those receiving neoadjuvant therapy were excluded. Patient and tumor characteristics evaluated included age, race, tumor size, grade, stage, histologic subtype, presence of lymphovascular invasion (LVI), estrogen (ER), progesterone (PR), and human epidermal growth factor receptor 2 (HER2) status. Results: BCS was performed in 1,889 and mastectomy in 1,078 patients. Breakdown by subtype included 2,201 (74%) patients with Luminal A, 344 (12%) with Luminal B, 144 (5%) with HER2, and 278 (9%) with TNBC. SNB was performed in 1,094 (37%), ALND in 756 (25%), and 1,117 (38%) patients had both. LN metastases were detected in 1050 (35%) patients. The LN positivity rate varied across subtypes with 734/2,201 (33%) in Luminal A, 143/344 (42%) in Luminal B, 108/278 (39%) in TNBC, and 65/144 (45%) in HER-2 (p = 0.0007). However, on multivariable analysis, there was no difference in LN positivity among subtypes (p=0.24). Only age < 50 (HR 1.5, CI 1.3 to 1.8), grade 2 or 3 tumors (HR 1.8, CI 1.4 to 2.5), size greater than 2cm (HR 3.2, CI 2.7 to 3.9), and presence of LVI (HR 3.9, CI 2.4 to 6.3) were significant predictors of LN positivity. Four or more involved nodes were seen most commonly in the HER2 (28/144; 19%) and Luminal B (47/344; 14%) subtypes, but not TNBC (26/278; 9%) or Luminal A (199/2201; 9%) (p < 0.0001). Conclusions: Predictors of LN metastases include younger age, higher grade, larger tumor size, and presence of LVI. Patients with TNBC are not more likely to have involved nodes than those with non-TNBC.