Abstract P4-08-27: The 21-gene Recurrence® (RS) Score assay in estrogen receptor positive node negative breast cancer: Real-world chemotherapy usage and patient characteristics within the intermediate and high-risk RS category
Authors: Le D , Chia S , Simmons C , Speers C , Gondara L , Nichol A , Lohrisch C , Gelmon KA 
Published: May 2019

Abstract
Background:
The Oncotype Dx, a 21-gene recurrence score (RS) assay, has been validated as a prognostic tool in early-stage, hormone receptor-positive, HER2-negative breast cancer. A RS of ≥ 31 is predictive for chemotherapy benefit. However, it has not been clearly established whether more intensive chemotherapy regimens for these patients provide further benefit and whether higher RS stratifications (≥41) influence treatment decisions.
Methods:
From the prospective British Columbia (BC) Breast Cancer Outcomes Unit database, we identified patients with N0 disease who received Oncotype Dx testing from May 2010 to December 2016. Patients with previous or synchronous breast cancer, and patients treated with neoadjuvant chemotherapy were excluded. Groups were defined that had an Oncotype Dx RS of 31-40 and ≥ 41. Demographic characteristics and type of chemotherapy received were collected. Additional subgroups were defined for patients who had a RS of 21-25 and who were ≤ 50 years old and &gt; 50 years old.
Results:
We identified 1,202 patients who received Oncotype Dx testing over the time period studied, with 14.8% (n=178) having a RS of ≥ 31. Among these high-risk patients, the median age was 58 (range 34-79), 90% received hormonal therapy and 85% received chemotherapy. In this cohort, 46% received docetaxel and cyclophosphamide for 4 cycles and 28% received 3rd generation chemotherapy. The use of 3rd generation chemotherapy in patients with a RS of ≥ 41 was significantly higher than in patients with RS between 31-40 (39% vs 22%, p = 0.006). Among patients who had a RS of 21-25 and who were ≤ 50 years old (n = 49), 53% received chemotherapy. Of patients who had a RS of 21-25 and who were &gt; 50 years old (n = 127), 16% received chemotherapy.
Conclusions:
Among patients with a RS ≥ 31, decisions regarding chemotherapy usage were heterogeneous with docetaxel and cyclophosphamide for 4 cycles being the most commonly used regimen. However, in those with a RS ≥ 41, 3rd generation chemotherapy was preferred. Patients with a RS between 21-25 and who were ≤ 50 years old received more chemotherapy than patients who were &gt; 50 years old.
RS 31-40 (n=116)RS ≥ 41 (n=62)RS ≥ 31 (n=178)Median age58.0 (range, 36-79)57.5 (range 34-78)58.0 (range 34-79)Pre-menopausal28.4%29.0%28.7%Hormonal therapy93.1%83.9%89.9%Chemotherapy86.2%82.3%84.8%DCx4 (1)54.3% (n=63/116) Median age 59.0 (range, 36 – 78)30.6% (n=19/62) Median age 64.0 (range, 42 – 78)46.1% (n=82/178) Median age 59.5 (range, 36 – 78)3rd generation chemo (2)21.6% (n=25/116) Median age 56.0 (range, 39 – 79)38.7% (n=24/62) Median age 52.0 (range, 34 – 76)27.5% (n=49/178) Median age 54.0 (range, 34 – 79)Other chemo10.3% (n=12/116) Median age 57.5 (range, 52 – 78)12.9% (n=8/62) Median age 64.0 (range, 42 – 72)11.2% (n=20/178) Median age 58.5 (range, 42 – 78)(1) Docetaxel and cyclophosphamide, 4 cycles (2) Anthracycline and Taxane containing regimens, 6 cycles or 8 cycles
Citation Format: Le D, Chia S, Simmons C, Speers C, Gondara L, Nichol A, Lohrisch C, Gelmon KA. The 21-gene Recurrence® (RS) Score assay in estrogen receptor positive node negative breast cancer: Real-world chemotherapy usage and patient characteristics within the intermediate and high-risk RS category [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-27.