Study population
Tumors, HER2-negative, tumor, advanced/metastatic disease
BREAST ADENOCARCINOMA, TUMOR, METASTATIC TUMOR, DISEASE, METASTATIC DISEASE, TUMORS, ONCOLOGY, PRIMARY TUMOR
The study population comprised postmenopausal women aged ≥ 20 years with a histological or cytological proven diagnosis of breast adenocarcinoma, with either evidence of locally advanced disease not amenable to radiation therapy or surgery in a curative intent, or inoperable and/or metastatic disease, with no standardized endocrine treatment option. Patients had previously received ≥ 6 months of endocrine therapy and no more than three chemotherapy regimens for advanced/metastatic disease.Patients were included in the study either after the primary tumor or metastatic site was confirmed to be (i) ER-positive (> 1% tumor cell staining by immunohistochemistry [IHC] or an Allred score of ≥ 3 by IHC); and (ii) HER2-negative (HER2 non-overexpressing by IHC [0, 1 +] or in situ hybridization-negative [single-probe average HER2 copy number < 4.0 signals/cell] or dual-probe HER2/centromeric probe for chromosome 17 ratio < 2 with an average HER2 copy number < 4.0 signals/cell as per the American Society of Clinical Oncology guidelines [Any measurable lesions (not mandatory) were assessed in accordance with Response Evaluation Criteria for Solid Tumors version 1.1 (RECIST v1.1). Patients were required to have an Eastern Cooperation Oncology Group performance status (PS) < 2. Patients did not enter the study if they had received curative radiotherapy within 3 weeks before the first administration of amcenestrant. Any patients who had previously received SERDs other than fulvestrant at any time, or fulvestrant within 6 weeks before the first administration of amcenestrant were excluded. Complete inclusion and exclusion criteria are reported in the supplementary material.In consenting patients, paired tumor samples were collected for molecular analysis from the start of treatment (use of most recent archived biopsy < 3 months of starting treatment or a fresh biopsy was collected at the start of treatment) and the end of cycle 2 (fresh biopsy collected from the primary or metastatic tumor).