Participants in this study were hormone-receptor-positive HER2-negative patients with advanced breast cancer who had previously used CDK4/6 inhibitors. Hormone receptor positive HER2 negative was defined as ER positive (IHC ER positive percentage > 10% or PR positive (IHC PR positive percentage > 10%) and HER2 negative (IHC-/+; Or IHC++ but FISH/CISH-).~The Department of Pathology and the Key Laboratory of Breast Cancer of Fudan University Shanghai Cancer Center conducted digital pathological typing of the biopsy pathology of metastatic lesions of all participants . If the pathology of metastatic lesions could not be obtained, the digital pathological typing was performed according to the pathology of primary lesions. According to the digital pathological types of biopsy tissue and peripheral blood ctDNA, the patients were divided into four precise subtypes: SNF1, SNF2, SNF3, and SNF4. At the same time, the negative control group was randomly set by subtype stratification at 2:1. In different SNF types, patients were divided into 7 subcohorts according to the genetic PANEL results.
The purpose of this study is to establish a prospective, single-center platform research based on clinical subtypes to explore precision therapy in patients hormone-receptor-positive HER2-negative advanced breast cancer who had previously used CDK4/6 inhibitors.