The combination of docetaxel, cisplatin, and fluorouracil (DCF) is highly synergistic in advanced gastric cancer. We aimed to explain these synergistic effects at the molecular level. Thus, we constructed a weighted correlation network using the differentially expressed genes between Stage I and IV gastric cancer based on The Cancer Genome Atlas (TCGA), and three modules were derived. Next, we investigated the correlation between the eigengene of the expression of the gene network modules and the chemotherapeutic drug response to DCF from the Genomics of Drug Sensitivity in Cancer (GDSC) database. The three modules were associated with functions related to cell migration, angiogenesis, and the immune response. The eigengenes of the three modules had a high correlation with DCF (−0.41, −0.40, and −0.15). The eigengenes of the three modules tended to increase as the stage increased. Advanced gastric cancer was affected by the interaction the among modules with three functions, namely cell migration, angiogenesis, and the immune response, all of which are related to metastasis. The weighted correlation network analysis model proved the complementary effects of DCF at the molecular level and thus, could be used as a unique methodology to determine the optimal combination of chemotherapy drugs for patients with gastric cancer.Although its incidence is decreasing in some parts of the world, gastric cancer is still the fourth most common cancer worldwide 1,2 . It poses a critical clinical challenge and is associated with poor prognosis, because a high percentage of patients are diagnosed at an advanced stage in some areas and due to its relatively chemoresistant properties and limited treatment options. Metastatic spread occurs frequently in advanced gastric cancer, and it is one of the major causes of death 3,4 . Systemic chemotherapy, which involves a combination of various cytotoxic agents, constitutes the main type of treatment in the adjuvant or palliative setting for patients with metastatic or recurrent cancer 5-7 . Thus far, the choices regarding chemotherapeutic agents or their combinations have typically been determined according to the results from clinical trials. Therefore, the accurate prediction of the response to combination chemotherapy is labor intensive, time consuming, and expensive because of the explosion in the number of combinations available 8 . Accordingly, a new methodology for conducting a molecular-level analysis in order to understand the association between advanced gastric cancer and chemotherapy sensitivity is required.Despite the increasing knowledge about tumor biology and pharmacology, our understanding of combination chemotherapy is limited due to the complex factors involved, such as the gene-drug interactions and gene regulatory networks 9 . Nonetheless, various combinations of chemotherapeutic drugs have been extensively tested, because they can increase efficacy, lower dosages, and minimize drug resistance. The combination of docetaxel, cisplatin, and 5-fluorouracil (DCF) is one ...