Circulating Sex Hormone Levels and Risk of Gastrointestinal Cancer: Systematic Review and Meta-Analysis of Prospective Studies

Background: Sex hormones may influence the development of gastrointestinal cancer, but evidence is inconsistent.Methods: We systematically searched MEDLINE and Embase databases to identify prospective studies examining associations between prediagnostic circulating levels of sex hormones and risk of five gastrointestinal cancers: esophageal, gastric, liver, pancreatic, and colorectal cancer. Pooled ORs and 95% confidence intervals (95% CI) were calculated using random-effects models.Results: Among 16,879 identified studies, 29 were included (11 cohort, 15 nested case-control, and three case-cohort studies). Comparing the highest versus lowest tertiles, levels of most sex hormones were not associated with the studied tumors. Higher levels of sex hormone binding globulin (SHBG) were associated with increased risk of gastric cancer (OR = 1.35; 95% CI, 1.06-1.72), but such associations were restricted in men only (OR = 1.43; 95% CI, 1.10-1.85) when stratified by sex. Higher SHBG levels were associated with increased risk of liver cancer (OR = 2.07; 95% CI, 1.40- 3.06). Higher testosterone levels were associated with increased risk of liver cancer overall (OR = 2.10; 95% CI, 1.48-2.96), particularly in men (OR = 2.63; 95% CI, 1.65-4.18), Asian populations (OR = 3.27; 95% CI, 1.57-6.83), and in hepatitis B surface antigen-positive individuals (OR = 3.90; 95% CI, 1.43-10.64). Higher levels of SHBG and testosterone were associated with decreased risk of colorectal cancer in men (OR = 0.89; 95% CI, 0.80-0.98 and OR = 0.88; 95% CI, 0.80-0.97, respectively) but not in women.Conclusions: Circulating levels of SHBG and testosterone may influence the risk of gastric, liver, and colorectal cancer.Impact: Further clarifying the role of sex hormones in the development of gastrointestinal cancer may unravel future novel targets for prevention and treatment.