Abstract PS4-28: Efficacy of adjuvant chemotherapy stratified by age and the 21 gene recurrence score in estrogen receptor positive breast cancer
Authors: Yu Jing , Lin Caijin , Huang Jiahui , Hong Jin , Gao Weiqi , Zhu Siji , Wang Hui , Huang Ou , Chen Xiaosong , He Jianrong , Zhu Li , Chen Weiguo , Li Yafen , Shen Kunwei , Wu Jiayi 
Published: February 2021

Abstract
Background: The 21-gene recurrence score (RS) can predict chemotherapy benefit in estrogen receptor (ER)-positive, human epidermal growth factor receptor-2 (HER2)-negative early breast cancer patients. The TAILORx showed that age would influence the interaction between RS and chemotherapy effect, and patients ≤50 years with RS &gt;15 can benefit from chemotherapy. The current study aimed to determine the RS threshold that can predict chemotherapy benefit in both young and elder women. Methods: Patients diagnosed with pN0-1, ER+/HER2- breast cancer between 2009 and 2016 at Shanghai Ruijin hospital were retrospectively reviewed. A one-to-one propensity score matching (PSM) was performed between women receiving chemotherapy or not. Patients were then stratified by different cutoffs of age (range, 30-65 years). In each prespecified strata of age, cox proportional hazards models were used to determine the RS threshold which was predictive of chemotherapy benefit. Results: A total of 1227 patients were included. The median age was 58 years and the median RS was 24. After matching, the RS values that can manifest the chemotherapy benefit varied with age. For patients at 55 years of age or younger, apparent chemotherapy benefit was observed in those who had RS &gt;25 (P = 0.03), with 4-year invasive disease-free survival (IDFS) rate of 97.0% and 89.3% in patients receiving chemotherapy or not. While patients derived no benefit from chemotherapy if they had RS ≤25 (P = 0.66, 4-year IDFS rate: 95.3% vs. 94.6%). However, for patients older than 55 years, adjuvant chemotherapy was associated with better prognosis in those with RS &gt;36 (P = 0.014, 4-year IDFS rate: 94.7% vs. 76.2%), but not in those having RS ≤36 (P = 0.13, 4-year IDFS rate: 92.3% vs. 95.8%). Conclusions: The RS threshold to demonstrate the chemotherapy benefit differed with age. Young patients with RS &gt;25 and old patients with RS &gt;36 could benefit from adjuvant chemotherapy.
Survival of breast cancer patients receiving adjuvant chemotherapy or not stratified by age and theChemoendocrine therapyEndocrine therapyP-value4-year IDFS rate (%)95% CI (%)4-year IDFS rate (%)95% CI (%)≤55 yearsRS ≤2595.390.7-100.094.689.6-100.00.66RS &gt;2597.091.3-100.089.382.0-97.30.03&gt;55 yearsRS ≤3692.387.7-97.295.892.1-99.60.13RS &gt;3694.787.9-100.076.252.1-100.00.014
Citation Format: Jing Yu, Caijin Lin, Jiahui Huang, Jin Hong, Weiqi Gao, Siji Zhu, Hui Wang, Ou Huang, Xiaosong Chen, Jianrong He, Li Zhu, Weiguo Chen, Yafen Li, Kunwei Shen, Jiayi Wu. Efficacy of adjuvant chemotherapy stratified by age and the 21 gene recurrence score in estrogen receptor positive breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-28.