Survival benefits of perioperative chemoradiotherapy versus chemotherapy for advanced stage gastric cancer based on directed acyclic graphs

The overall survival benefits of perioperative chemotherapy (PCT) and perioperative chemoradiotherapy (PCRT) for patients with locally advanced gastric cancer (GC) have not been fully explored. The aim of this study was to compare the benefits of PCT and PCRT in GC patients and determine the factors affecting survival rate using directed acyclic graphs (DAGs). The data of 1,442 patients with stage II-IV GC who received PCT or PCRT from 2000 to 2018 were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database. First, the least absolute shrinkage and selection operator (LASSO) was used to identify possible influencing factors for overall survival. Second, the variables that were selected by LASSO were then used in univariate and Cox regression analyses. Third, corrective analyses for confounding factors were selected based on DAGs that show the possible association between advanced GC patients and outcomes and evaluate the prognosis. Patients who received PCRT had longer overall survival than those who received PCT treatment (P = 0.015). The median length of overall survival of the PCRT group was 36.5 (15.0 − 53.0) months longer than that of the PCT group (34.6 (16.0 − 48.0) months). PCRT is more likely to benefit patients who are aged ≤ 65, male, white, and have regional tumors (P<0.05). The multivariate Cox regression model showed that male sex, widowed status, signet ring cell carcinoma, and lung metastases were independent risk factors for a poor prognosis. According to DAG, age, race, and Lauren type may be confounding factors that affect the prognosis of advanced GC. Compared to PCT, PCRT has more survival benefits for patients with locally advanced GC, and ongoing investigations are needed to better determine the optimal treatment. Furthermore, DAGs are a useful tool for contending with confounding and selection biases to ensure the proper implementation of high-quality research.