Abstract 4713: Serum thyroglobulin, a biomarker for iodine deficiency, and risk of upper gastrointestinal cancers

Objectives: Gastric cancer is the second leading cause of cancer death worldwide and has been hypothesized to be associated with iodine deficiency. While iodine concentrations are highest in the thyroid, iodine also concentrates in gastric tissue where it may act as an antioxidant for the stomach and possibly the esophagus. We previously showed that self-reported goiter was associated with significantly increased risk of gastric noncardia adenocarcinoma (GNCA) and non-significantly increased risks of gastric cardia adenocarcinoma (GCA) and esophageal squamous cell carcinoma (ESCC). Iodine deficiency is correlated with increased serum thyroglobulin, and this study aimed to determine whether serum thyroglobulin is associated with GNCA, GCA, and ESCC in a Chinese population with very high rates of upper gastrointestinal (UGI) cancers. Methods: We examined the association between serum thyroglobulin levels and the three UGI cancers in a study nested in the Linxian General Population Nutrition Intervention Trial. At baseline, blood was drawn from participants, ages 40-69 years, and outcomes were identified during 15 years of follow-up. Approximately 200 subjects of each case type and 400 non-case controls were selected for serum thyroglobulin concentration measurements. All samples were first screened for thyroglobulin antibody, and thyroglobulin concentrations were then measured by radioimmunoassay (RIA) for thyroglobulin-antibody-positive samples or by immunometric assay (IMA) for thyroglobulin-antibody-negative samples. Thyroglobulin concentrations were analyzed as quartiles using logistic regression models adjusted for numerous potentially confounding factors. Results: 25% of females and 5% of males in the controls were thyroglobulin-antibody-positive. Compared to participants in the lowest quartile, those in the highest quartile of serum thyroglobulin had adjusted odds ratios of 0.82 (95% confidence interval 0.50-1.36) for GNCA, 1.12 (0.66-1.90) for GCA, and 0.73 (0.44-1.21) for ESCC. Conclusions: Using serum thyroglobulin, a sensitive biomarker of iodine deficiency, we found no association between serum thyroglobulin concentrations and risk of UGI cancer in the overall study population. Our results do not support the hypothesis that iodine deficiency is associated with an increased risk of UGI cancers in this population. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4713.