4185 Background: Gastroesophageal tumors are some of the most highly prevalent cancers worldwide. Despite the high prevalence and advancement in treatments, they represent a major cause of cancer-related deaths. Thus, advancement in gastroesophageal cancer treatment and post-treatment monitoring are imperative in improving disease prognosis. In this study, we aimed to investigate the association between pre- or post-treatment plasma circulating tumor deoxyribonucleic acid (ctDNA) and post-treatment outcomes. Methods: We searched PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), and Scopus on October 30, 2025 using ctDNA and gastroesophageal cancer as the keywords along with their related MeSH terms. Studies were included if they investigated the association between the detection of pre- or post-treatment plasma ctDNA and disease outcomes among patients with esophageal or gastric cancer. Our exposure of interest was the detection of pre- or post-treatment ctDNA in plasma while the outcomes of interest were tumor recurrence and tumor progression. The odds ratio (OR) and its 95% confidence interval (95%CI) were the effect measures of choice in the analysis. Results: We included a total of 1,897 patients with gastric or esophageal cancer from 21 prospective or retrospective cohorts. Our analysis revealed that pre-treatment detection of ctDNA in the plasma was associated with higher odds of tumor recurrence (OR=4.37; 95%CI: 1.20-15.92) and progression (OR=4.80; 95%CI: 2.51-9.18). These results were consistent in the subgroup analysis among patients with esophageal cancer while they lost their significance among patients with gastric cancer and among good quality studies (Newcastle Ottawa Scale>5). Moreover, the detection of post-treatment ctDNA was associated with higher odds of tumor recurrence (OR=6.14; 95%CI: 3.79-9.94) and progression (OR=8.28; 95%CI: 5.03-13.64). These results were consistent in the subgroup analysis of patients with esophageal cancer, gastric cancer and among good quality studies. Conclusions: Our results highlight that detection of pre-treatment but more so post-treatment ctDNA is associated with post-treatment cancer outcomes. Our results emphasize the potential use of ctDNA as a valuable tool for detection of early gastroesophageal cancer recurrence and post-treatment progression.
Al-Sayegh et al. (Wed,) studied this question.