Cancer Genetics and Epigenetics 2024, Vol.12, No.1, 37-46 http://www.medscipublisher.com/index.php/cge 39 1.2 Limitations and challenges of traditional methods While traditional diagnostic methods have played a crucial role in the diagnosis of gastric cancer, they also have some limitations and challenges. Firstly, although endoscopic examination allows for direct observation of the stomach, it may be challenging to detect tumors located deep within the gastric wall or early-stage gastric cancer. Additionally, endoscopic examination relies on the experience and technical proficiency of the physician, leading to potential variations in diagnostic results among different physicians. The limitations of barium meal X-ray examination lie in its lower sensitivity for the diagnosis of early gastric cancer. Early gastric cancer often manifests as subtle mucosal changes that are challenging to accurately capture in X-ray images. Additionally, barium meal examinations cause considerable discomfort to patients and do not allow for biopsy procedures. Regarding the application of tumor markers, although certain markers such as CA-19-9, CEA, etc., may elevate in gastric cancer patients, they lack specificity for gastric cancer and may show abnormalities in various other diseases. Therefore, they cannot serve as standalone diagnostic tools but rather function as supplementary diagnostic measures. Furthermore, traditional diagnostic methods often fail to detect tumors in the early stages of gastric cancer. By the time symptoms appear, the majority of gastric cancer patients are already in the middle to late stages, presenting greater treatment challenges and poorer prognoses. Hence, the development of more efficient and sensitive early diagnostic methods is a key focus in current gastric cancer research. 2 Application of Molecular Markers in Gastric Cancer Diagnosis Molecular markers demonstrate significant potential in the early diagnosis of gastric cancer, but they still need to overcome numerous challenges to achieve widespread application in clinical practice. Future research efforts should focus on improving the specificity and sensitivity of molecular markers, reducing detection costs, and conducting large-scale clinical validations to better translate these new findings into the early diagnosis and treatment of gastric cancer patients. 2.1 Definition and classification of molecular markers Molecular markers refer to molecules that can be detected and quantified within a biological organism, and they can include proteins, nucleic acids, small-molecule metabolites, or cells. In the medical field, molecular markers are utilized for disease diagnosis, prognosis assessment, treatment efficacy monitoring, and predicting disease risks. Molecular markers can be categorized based on their biological characteristics, such as gene markers, protein markers, and metabolic markers. In gastric cancer research, these molecular markers play a crucial role in identifying the early stages of the disease, assessing disease progression, guiding treatment decisions, and monitoring treatment efficacy. 2.2 Key molecular markers discovered in early diagnosis of gastric cancer in recent years In recent years, with the rapid development of molecular biology and genomics, numerous novel molecular markers have been discovered and applied in the early diagnosis of gastric cancer. For instance, gene mutation markers such as HER2/neu, EGFR, KRAS, among others, have been confirmed to play crucial roles in the occurrence and development of gastric cancer (Chen et al., 2019). Overexpression of the HER2/neu protein is associated with the development of gastric cancer, while mutations in the EGFR and KRAS genes are closely linked to the invasiveness and prognosis of gastric cancer. Additionally, microRNAs (miRNAs) have been found to play a significant role in the development of gastric cancer. Specific miRNA expression patterns can serve as potential biomarkers for the early diagnosis of gastric cancer. For example, altered expression levels of miR-21, miR-223, and miR-451 in gastric cancer patients can be used for auxiliary diagnosis. Similarly, protein markers such as gastric proenzyme, vascular endothelial growth factor (VEGF), and tumor necrosis factor (TNF) have also been studied for early detection of gastric cancer.
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