Favorable locoregional control in clinically node-negative hormone-receptor positive breast cancer with low 21-gene recurrence scores: a single-institution study with 10-year follow-up

Abstract

Background Recent studies have shown a lower likelihood of locoregional recurrences in patients with a low 21-gene recurrence score (RS). In this single-institution study, we investigated whether there are any associations between different cutoff values of 21-gene RS, histopathological factors, and outcome in patients with long-term follow-up. Methods The study included 61 patients who had early-stage (I-II) clinically node-negative hormone receptor-positive and HER2-negative breast cancer and were tested with the 21-gene RS assay between February 2010 and February 2013. Demographic, clinicopathological, treatment, and outcome characteristics were analyzed. Results The median age was 48 years (range, 29-72 years). Patients with high histologic grade (HG), Ki-67 >= 25\%, or Ki-67 >= 30\% were more likely to have intermediate/high RS (>= 18). Based on the 21-gene RS assay, only 19 patients (31\%) received adjuvant chemotherapy. At a median follow-up of 112 months, 3 patients developed locoregional recurrences (4.9\%), which were treated with endocrine therapy alone. Among patients treated with endocrine treatment alone (n = 42), the following clinicopathological characteristics were not found to be significantly associated with 10-year locoregional recurrence free survival (LRRFS): age < 40 years, age < 50 years, high histological or nuclear grade, high Ki-67-scores (>= 15\%, >= 20\%, >= 25\%, >= 30\%), presence of lymphovascular invasion, luminal-A type, multifocality, lymph node positivity, tumor size more than 2 cm, RS >= 18, and RS > 11. However, patients with RS >= 16 had significantly poorer 10-year LRRFS compared to those with RS < 16 (75\% vs. 100\%, respectivelyp = 0.039). Conclusions The results suggest that patients with clinically node-negative disease and RS >= 16 are more likely to benefit from adjuvant chemotherapies. However, those with RS < 16 have an excellent outcome and local control in long-term follow-up with endocrine treatment alone.