What this Trial Is About

Researchers are investigating hormone receptor-positive HER2-negative breast cancer patients who are starting treatment with CDK4/6 inhibitors, either for advanced metastatic disease or as adjuvant therapy in early high-risk cases. The study aims to explore the relationship between the gut microbiome, circulating immune and metabolic biomarkers, and how patients respond to CDK4/6 inhibitor therapy. The goal is to identify microbial, immune, or metabolic biomarkers from stool or blood samples that can predict treatment outcomes and support new combination treatment strategies for patients with poor prognosis. Participants will receive CDK4/6 inhibitors combined with endocrine therapy, such as aromatase inhibitors, fulvestrant, or tamoxifen, depending on their disease stage. The study includes two cohorts: patients with untreated advanced breast cancer starting first-line CDK4/6 inhibitor therapy, and patients with early breast cancer at high risk of relapse receiving adjuvant CDK4/6 inhibitor treatment. Paraffin-embedded tumor tissue samples are required for inclusion, and treatment will be monitored throughout the study period. During the study, researchers will collect stool and blood samples to analyze gut microbiome composition, immune cell populations, metabolic profiles, and cytokine levels before and during treatment. These assessments aim to correlate biological markers with clinical outcomes to CDK4/6 inhibitor therapy. Participants will be monitored for adherence and safety, with data gathered to generate hypotheses for future combination therapy trials. The study involves ongoing sample collection and clinical evaluations to understand mechanisms influencing treatment response.

A Study of the Gut Microbiome in Hormone Receptor-positive HER2-negative Breast Cancer Treated With CDK4/6 Inhibitors