This prospective observational study aims to evaluate serum levels of PTEN, a tumor suppressor gene, and organ-specific microRNAs (miRNAs) associated with metastatic patterns in breast cancer. Serum samples will be analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR)-based miRNA profiling and enzyme-linked immunosorbent assay (ELISA)-based PTEN quantification. Three groups will be included: patients with metastatic breast cancer (n=80), patients with non-metastatic early-stage breast cancer (n=40), and healthy controls (n=40).

The primary objective is to identify serum biomarkers that differentiate metastatic from non-metastatic disease. Secondary analyses will evaluate correlations between biomarker levels and organ-specific metastatic involvement, including bone, lung, liver, and brain metastases. Findings from this study may support the development of a noninvasive serum-based tool for predicting metastatic patterns in breast cancer.

Breast cancer is a heterogeneous disease with varying biological behaviors and a strong tendency to metastasize to specific organs, including the bone, liver, lung, and brain. The development of distant metastases remains the primary cause of breast cancer-related mortality. Therefore, the identification of reliable, minimally invasive biomarkers that can predict metastatic spread is a critical unmet clinical need.

MicroRNAs (miRNAs) are small, noncoding RNA molecules that regulate gene expression and have emerged as promising biomarkers due to their stability in the circulation and their association with cancer progression. Specific miRNA expression patterns have been linked to organotropism in breast cancer, including signatures associated with bone, lung, liver, and brain metastases. Additionally, PTEN is a key tumor suppressor gene involved in cell cycle regulation, apoptosis, and PI3K/AKT pathway signaling. Loss of PTEN function is frequently observed in aggressive and metastatic breast cancers, and reduced circulating PTEN levels may correlate with tumor burden and metastatic dissemination.

This prospective observational clinical study aims to evaluate serum PTEN levels and organ-specific miRNA profiles in three participant groups:

Metastatic breast cancer patients (n=80) diagnosed with distant organ involvement.

Early-stage non-metastatic breast cancer patients (n=40) with no radiological or clinical evidence of metastasis.

Healthy control participants (n=40) without known malignancy.

Serum samples will undergo laboratory analysis using two validated molecular techniques:

Quantitative reverse transcription polymerase chain reaction (qRT-PCR) for profiling selected miRNAs associated with organ-specific metastatic patterns.

Enzyme-linked immunosorbent assay (ELISA) for quantification of circulating PTEN protein levels.

The primary objective of the study is to compare serum PTEN and miRNA expression levels between metastatic and non-metastatic breast cancer groups, as well as healthy controls. Secondary objectives include assessing associations between these biomarkers and (a) the number of metastatic sites, (b) specific organ involvement (bone, lung, liver, brain), and (c) selected clinical characteristics, including hormone receptor status, HER2 expression, patient age, and stage at diagnosis.

The overarching goal is to characterize a panel of circulating biomarkers that may contribute to early detection of metastatic potential and organ-specific metastatic patterns in breast cancer. Identifying such signatures may facilitate noninvasive risk stratification, support personalized treatment planning, and form the basis for future translational research aimed at developing clinically applicable diagnostic assay

Inclusion Criteria:

• Female individuals aged ≥18 years
• Ability to provide written informed consent
• Group I (Metastatic BC): Histopathologically confirmed breast cancer and radiologically or clinically proven distant organ metastasis at the time of enrollment
• Group II (Non-Metastatic BC): Histopathologically confirmed breast cancer with no evidence of distant metastasis
• Group III (Healthy Controls): Women ≥18 years with no known breast disease and no personal history of malignancy

Exclusion Criteria:

• History of any other primary malignancy
• Known breast disease or breast cancer diagnosis in Group III
• Immunosuppressive therapy that may alter immune or biomarker profiles
• Active infection or inflammatory condition that may alter biomarker levels
• Inability or unwillingness to provide informed consent
• Severe hepatic, renal, or hematologic dysfunction
• Current pregnancy or lactation

Three groups were included in this study: women with metastatic breast cancer, women with early or locally advanced nonmetastatic breast cancer, and age-matched healthy female controls.

Participants in the metastatic group have radiologically or clinically confirmed distant organ involvement. The nonmetastatic group includes patients with histopathologically confirmed breast cancer without any evidence of distant metastasis. Healthy controls consist of women without known breast disease, malignancy, or systemic illness. All participants are aged 18 years or older and able to provide informed consent. Recruitment will occur through oncology clinics, breast surgery units, and outpatient services.

Individual participant data (IPD) will not be shared due to privacy and data protection regulations. Only de-identified, aggregate results may be shared with researchers upon reasonable request.