Breast carcinoma with 21-gene recurrence score lower than 18: rate of locoregional recurrence in a large series with clinical follow-up

Background The 21-gene recurrence score (RS) assay determines the benefit of adding chemotherapy to endocrine therapy for patients with early stage, estrogen receptor (ER)-positive, HER2-negative breast cancer. The RS risk groups predict the likelihood of distant recurrence and have recently been associated with an increased risk of locoregional recurrence (LRR). This study analyzed clinicopathologic features of patients with low RS and LRR. Methods In our institutional database, we identified 1396 consecutive female patients with lymph node negative, ER+/HER2- invasive breast carcinoma and low RS (