LAUSR

Introduction: The 21-gene Recurrence Score (RS) assay has been shown in retrospective studies to predict benefit of adjuvant chemotherapy (AC) in node positive (N+) breast cancer (BC) patients (pts). This study evaluates the trends and patterns of use of RS assay in N+, ER+/HER2-breast cancer and the impact of RS on decision to use AC in a real-world multi-institutional database. Methods: Pts with T1-T4c, N1mi-N3, ER+/HER2- BC diagnosed between 2010 and 2013, included in the National Cancer Data Base were analyzed. Pts who received neo-AC were excluded. Analyses included Cochrane-Armitage tests for trends and multivariable logistic regression assessing factors influencing RS testing and AC recommendations based on RS. Results: Among 73,049 pts, RS was obtained in 20.6%, increasing from 14.9% in 2010 to 24.4% in 2013 (p 85%) with RS 26-30 or high risk RS were recommended AC regardless of N stage. For pts with low risk RS, recommendation for AC increased significantly with increasing N stage (see table). On multivariable analysis, in pts with low risk RS, AC was more likely to be recommended in those with N1/N2+ stage (OR 2.3 and 9.1 vs N1mi), T2 and T3/T4 tumors (OR 1.3 and 2.2 vs T1 tumors), poorly differentiated tumors (OR 1.6) and younger age (OR 3.4 and 1.7, respectively, for Conclusions: RS was obtained in about one fifth of pts with N+ ER+/HER2- BC, predominantly for N1mi and N1 disease. Overall, RS testing decreased frequency of recommendation of AC in N+ BC pts. The RS influenced use of AC particularly in N1mi and N1 pts, likely avoiding overtreatment of those with low risk RS and RS 18-25. Prospective data regarding RS to direct AC in N+ BC are awaited. Citation Format: Peethambaram PP, Hoskin TL, Heins CN, Habermann EB, Boughey JC. How 21-gene recurrence score assay is being used to individualize adjuvant chemotherapy recommendations in ER+/HER2 -node positive breast cancer -A national cancer data base study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr PD7-05.