This study is a prospective, observational clinical research aimed at establishing a multimodal database encompassing clinical information and gut microbiome data from a sample of over 1,000 breast cancer patients comorbid with depression. The research involves collecting cohort sample information from breast cancer patients with comorbid depression, as well as fecal, blood, and saliva specimens for metagenomic sequencing, untargeted metabolite detection, and cortisol level analysis, respectively. Based on the collected multimodal data, diagnostic, efficacy prediction, and prognostic survival prediction models for breast cancer with comorbid depression will be developed. Additionally, a precision prediction cloud platform will be designed and deployed to support data upload, model prediction, and result visualization.

Inclusion Criteria:

• Pathologically confirmed primary breast cancer; Aged 18-80 years; No prior history of malignancy other than breast cancer; Awareness of their breast cancer diagnosis; Karnofsky Performance Status (KPS) score >70; Willing to provide blood, fecal, and saliva samples with signed informed consent.

Exclusion Criteria:

• Physician-diagnosed mental disorders before or after breast cancer diagnosis; Severe chronic somatic diseases (e.g., central nervous system disorders, severe head trauma, substance abuse/dependence, intellectual disability, diabetes, gynecological diseases, cardiovascular diseases, thyroid disorders, etc.); Presence of two or more primary malignancies of different tissue origins; Central nervous system (CNS) metastasis of breast cancer; Clinically diagnosed digestive system diseases (e.g., enteritis, gastritis); Use of antidepressant or anxiolytic therapy during the study; Use of medications that alter gut function or metabolism during the study; Pregnant or lactating women; Radiotherapy or chemotherapy within the past 21 days; Use of antibiotics, probiotics, prebiotics, or synbiotics within 3 months prior to the study; Other reasons deemed unsuitable for participation by investigators.

patients with breast cancer