Association Between Gastroesophageal Reflux Disease and Extraesophageal Malignancies: A Systematic Review and Meta-Analysis

Background/Objectives: The association between gastroesophageal reflux disease (GERD) and extraesophageal malignancies remains unclear. This study aimed to systematically evaluate the relationship between GERD and these cancers. Methods: PubMed, Embase, Scopus, Cochrane Library, and Web of Science were searched for studies reporting risk estimates—risk ratios (RRs), odds ratios (ORs), hazard ratios (HRs), or standardized incidence ratios (SIRs)—of GERD and extraesophageal malignancies. Mendelian randomization (MR) studies with available risk estimates and 95% confidence intervals (CIs) were also included. Pooled estimates with 95% CIs were calculated using a random-effects model. Results: As of 21 May 2025, a total of 37 studies were included in the analysis. GERD was significantly associated with an increased risk of several extraesophageal malignancies, including pharyngeal cancer (pooled RR = 2.04; 95% CI: 1.38–3.02), with a particularly high risk observed for hypopharyngeal cancer (RR = 2.95; 95% CI: 1.99–4.37; I2 = 60.24%). Elevated risks were also identified for laryngeal cancer (RR = 2.23; 95% CI: 1.41–3.52) and lung cancer (RR = 1.20; 95% CI: 1.01–1.42). No significant association was found between GERD and colorectal cancer (RR = 1.19; 95% CI: 0.68–2.09), and findings regarding oral cancer were inconsistent across studies. Six MR studies confirmed a positive causal relationship between GERD and lung cancer, while one MR study suggested a potential causal association with oral cancer and another with pancreatic cancer. Conclusions: Our findings suggest that GERD may be a significant risk factor for pharyngeal, laryngeal and lung cancers. Appropriate evaluation and surveillance in patients with GERD may be warranted.