Abstract P2-11-31: FAVORABLE LOCOREGIONAL CONTROL IN CLINICALLY NODE-NEGATIVE HORMONE-RECEPTOR POSITIVE BREAST CANCER WITH LOW 21-GENE RECURRENCE SCORES: A SINGLE INSTITUTIONAL STUDY WITH 10-YEAR FOLLOW-UP
Authors: Uras Cihan , Cabıoğlu Neslihan , Tokat Fatma , Kara Halil , ER Ozlem , Korkmaz Taner , Bese Nuran , Ince Umit 
Published: March 2023

Abstract
Background: Recent studies have shown a lower likelihood of locoregional recurrences in patients with low 21-gene recurrence score (RS). In this single institutional study, we investigated any associations between different cut-off values of 21-gene RS and histopathological factors and outcome in patients with long-term follow-up.
Methods: Between February 2010 to February 2013, 61 patients with early stage clinically node-negative hormone receptor-positive and HER2-negative breast cancer tested for the 21-gene RS assay, were included into the study. The clinicopathological, treatment and outcome characteristics were analyzed.
Results: Median age was 48 (range, 29-72). Of those, 53 patients were diagnosed with Stage 1 (86.9%) and 8 patients were Stage 2 (13.1%) following surgery. Patients with high histologic grade (HG), or with Ki-67&gt;=25% were significantly more likely to have intermediate/high RS based on RS &gt;11 and &gt;18 (Table 1). 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 local recurrences (4.9%) treated with endocrine therapy alone. Among patients treated with endocrine treatment alone (n=42), the clinicopathological characteristics including age &lt; 40, age &lt; 50, high histologic or nuclear grade, high Ki67-scores (&gt;=20%, &gt;=25%, &gt;=30%), presence of lymphovascular invasion, luminal-A type tumor, multifocality, lymph node positivity, tumor size more than 2 cm, RS&gt;=18 or RS&gt;11 were not significantly found to be associated with 10-year locoregional recurrence free survival (LRRFS). However, patients with a RS &gt;=16 have significantly shown a poorer 10-year LRRFS cpmpared to those with RS &lt; 16 (RS &lt; 16; 100% vs RS&gt;=16; 75%, p=0.039, Table 2).
Conclusions: These results suggest that Oncotype DX assay may be of little value in patients with high histologic grade or high Ki67 scores (&gt;= 25%) as treatment decision criteria to determine any benefit from chemotherapy. Furthermore, patients with a RS &gt;=16 are more likely to benefit from adjuvant chemotherapies, whereas those with a RS &lt; 16 have an excellent outcome and local control on long term follow-up with endocrine treatment alone. Further prospective studies should be performed to validate these findings in future.
Table 1. Correlation of 21-gene Recurrence Score (RS) including different cut-off values with Ki-67 scores and histopathological factors
Table 2. Clinicopathologic factors and 21-gene Recurrence Score (=RS) associated with disease free survival (DFS) and locoregional recurrence free survival free survival (=LRRFS). (DFS is equal to LRRFS since none of the patients developed distant metastases)
Citation Format: Cihan Uras, Neslihan Cabıoğlu, Fatma Tokat, Halil Kara, Ozlem ER, Taner Korkmaz, Nuran Bese, Umit Ince. FAVORABLE LOCOREGIONAL CONTROL IN CLINICALLY NODE-NEGATIVE HORMONE-RECEPTOR POSITIVE BREAST CANCER WITH LOW 21-GENE RECURRENCE SCORES: A SINGLE INSTITUTIONAL STUDY WITH 10-YEAR FOLLOW-UP [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-11-31.