INTRODUCTION: This study aimed to assess the expression changes of BTG1, PGI, and PGII in tissues and serum of patients with gastric cancer, atrophic gastritis, and healthy individuals. METHODS: QRT-PCR was used to measure BTG1, PGI, and PGII expression in 30 cancers, 30 atrophic gastritis, and 30 healthy tissue samples. Serum levels of PGI and PGII were measured using ELISA. Statistical tests included the Mann-Whitney U and independent T-test. Covariates like tumour stage and RESULTS: BTG1 expression was significantly lower in cancer and gastritis tissues. Serum PGI and PGII levels were significantly reduced in cancer patients ( DISCUSSION: The PGI/PGII ratio in serum emerged as a strong non-invasive biomarker for distinguishing cancer from healthy individuals. While BTG1 provides insights into gastric carcinogenesis, its clinical utility is limited due to the need for tissue samples. The serum-based PGI/PGII ratio shows greater promise as a non-invasive screening tool for GC.