Abstract PO2-16-08: Adjuvant Treatment Selection for County-Level Patients with HR+/HER2- Early Breast Cancer in a Real-Life Setting in China

Abstract Background: CHASE001 (NCT05544123), a prospective, non-interventional multicenter study exploring real-world treatment and referral behavior of Chinese county patients (pts) with HER2+ or HR+/HER2– breast cancer is ongoing since September 2022. A prespecified interim analysis (IA) on 750 HER2+ and HR+/HER2- early breast cancer (eBC) was reported at the ESMO Congress 2023. In the 2nd IA from CHASE001, adjuvant treatment selection for patients with HR+/HER2- eBC will be evaluated. Methods: The study was designed to enroll 2500 pts, including four cohorts (HER2+ eBC, HR+/HER2-eBC, HER2+ advanced BC, and HR+/HER2- aBC). In this IA, HR+/HER2- eBC pts after surgery were included. Descriptive statistics reported patient demographics, clinical and disease characteristics and treatment patterns. To investigate the factors associated with chemotherapy-free regimen, non-anthracycline chemotherapy regimen and ovarian function suppression (OFS), univariate and multivariate logistic regression analyses were conducted. Results: At data cutoff (May 17, 2023), 697 HR+/HER2- eBC pts (median age 52 years, 45.77% pT2, 50.93% pN0, 56.10% G2) were included from 26 institutions in China county areas, 338 (48.49%) were premenopausal. 584 (83.79%) received adjuvant chemotherapy, with a few (47/584, 8.05%) initially developing their treatment plan at a higher level hospital (national or provincial tertiary hospital). AC-T (309/584, 52.91%) was the most commonly used regimen. 181 (30.99%) pts received non-anthracycline chemotherapy regimen (mainly TC), and pts with N0, age≥65 years and ki67 < 20% had the strongest association to this regimen (multivariate OR=0.082, 95%CI [0.037,0.179], OR=0.463, 95%CI [0.250,0.859], and OR=0.642, 95%CI [0.418,0.985], respectively). Interestingly, on univariate analysis pts initially diagnosed in a higher level hospital were significantly associated with non-anthracycline regimen (P=0.0109), however on multivariate analysis it was no longer significant. 483 pts received endocrine therapy, including 234 (48.45%) premenopausal pts. The most commonly used endocrine regimen for premenopausal pts was OFS/OFS+ (122/234, 52.14%) ,of which half (61, 50%) were prescribed OFS+TAM/TOR; followed by TAM/TOR monotherapy (69/234, 29.49%). The proportions of patients classified as low, intermediate, and high clinical risk for recurrence (investigator assessed)were 33.62%, 42.67% and 23.71%. The OFS rate were 39.74% in low, 61.62% in intermediate and 70.91% in high risk pts, respectively. Multivariable analyses found that high clinical risk, age < 45 years and ki67 < 20% were strongly associated with the use of OFS (OR=0.210, 95%CI [0.066,0.674], OR=0.327, 95%CI [0.165,0.649], and OR=0.405, 95%CI [0.194,0.845], respectively). For postmenopausal pts, AI monotherapy (84.74%) was the most commonly used endocrine regimen. Conclusions: To our knowledge, this is the first real-world study evaluating the treatment patterns and referral behavior of BC pts in China counties. The 2nd IA results presented showed the current systemic adjuvant treatment preferences and influence factors from a large sample of HR+/HER2- eBC pts in China counties, which were generally consistent with China BC treatment guidelines. Table 1. Utilization of adjuvant systemic therapy regimens in 697 HR+/HER2− eBC pts, China counties AC-T: (dd)doxorubicin/epirubicin, cyclophosphamide, followed by (dd)paclitaxel/docetaxel; TC: paclitaxel/docetaxel, cyclophosphamide; AC: doxorubicin/epirubicin, cyclophosphamide; TAC: docetaxel, doxorubicin/epirubicin, cyclophosphamide; TAM: tamoxifen; OFS: ovarian function suppression; AI: aromatase inhibitors; TOR: toremifene; CDK4/6i: cyclin-dependent kinase 4/6 inhibitors; “Other” category includes various therapies used in <1% of patients each Citation Format: Yinghua Ji, Honglan Qu, Feidu Zhou, Juan Wang, Qianfu Wu, Guohua Dai, Mengyou Liu, Wenbo He, Wei Liang, Qiuli Meng, Yun Ren, Guoxiang Luo, Hongjian Wang, Hui Liu, Zien Qin, Yingguo Tian, Huali Tang, Hongmei Liu, Jun Luo, Zengfeng Yu, Guinv Hu, Jianzhi Gao, Xiang Tan, Yi Liu, Yuanjiang Zhang, Ming Wang, Min Zhang, Ping Lu. Adjuvant Treatment Selection for County-Level Patients with HR+/HER2- Early Breast Cancer in a Real-Life Setting in China [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-16-08.