The aim of this study was to identify and quantify microplastics in blood, stool, and tumor surgical specimens from gastric cancer patients by analyzing the nature, type, and abundance of microplastics using laser direct infrared (LDIR) spectroscopy, scanning electron microscopy (SEM), and pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Meanwhile, combining macro-genomic and metabolomic techniques to explore the association between microplastics and host microbiota and metabolic profiles, and to reveal the potential effects of microplastics on gastric cancer incidence and development will provide new insights into the relationship between microplastic contamination and gastric cancer, as well as an important scientific basis for future public health strategies and cancer prevention and control measures.

This This study is planned to collect blood, cancer and paracancer tissues, and stool samples from 20 patients with gastric cancer, 2 gastric cancer tissues (at least 1cm^3 each), 2 gastric paracancer tissues (at least 1cm^3 each), 2 venous bloods (5ml each), and 1 stool (at least 10g each) from each patient. Samples will be collected from December 2024 through November 2025, with an expected total of 140 samples. Sample collection, transportation, and storage are described in IV.2. & 3. Samples will be analyzed for the type, nature, and abundance of microplastics by Laser Direct Infrared Spectroscopy (LDIR), Scanning Electron Microscopy (SEM), and Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC/MS), which is expected to detect microplastics such as polyamides, polyethylene terephthalate (PET), and polyvinyl chloride (PVC). At the same time, blood and tissue samples will be metabolomically assayed using NNR-IVD technology and macro-genomic sequencing will be performed to explore potential associations between microplastics and microbiota and metabolic pathways in gastric cancer patients. By analyzing the distribution characteristics of microplastics in gastric cancer patients and their relationship with microbial communities and metabolic pathways, this study will reveal the impact of microplastics on the tumor microenvironment and further understand their role in gastric cancer development and progression.

Inclusion Criteria:

• age ≥18 years old;
• diagnosed with gastric cancer by pathology before surgery and not receiving chemotherapy, radiotherapy or immunotherapy;
• no history of other gastrointestinal diseases;
• complete clinical data and basic information;
• willing to participate in this study and sign an informed consent form.

Exclusion Criteria:

• Patients receiving neoadjuvant radiotherapy or chemotherapy;
• patients with other malignant tumors other than gastric cancer;
• patients with incomplete or unclear pathological data;
• individuals who are not willing to participate in the study.

Patients diagnosed with colorectal cancer by pathological biopsy were included in the study.

Data sharing is not permitted by the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University.