Abstract 6190: Descriptive analysis of selenium levels in a healthy Malawian subpopulation: Findings from a control study on esophageal squamous cell carcinoma (ESCC)

Background: Esophageal squamous cell carcinoma (ESCC) is the third most common cancer in Malawi, with an estimated 1,871 new cases and 1,766 deaths in 2024 in Malawi. Although drinking alcohol and smoking tobacco are major causes of ESCC in some populations, the high rates in Malawi are unlikely to be due to these agents. Several East African countries have high incidence rates of ESCC and low soil selenium concentrations. Observational and intervention studies in East Asia have shown that low selenium concentrations are linked to an increased risk of ESCC. Methods: We used control subjects from a previously reported hospital-based case-control study of ESCC conducted at two hospitals in Lilongwe, Malawi (2017-2020). The study collected questionnaire data and stored fractionated blood. ESCC cases were excluded due to reverse causation for nutritional biomarkers. Instrumental neutron activation analysis (INAA) was used to measure serum selenium concentrations. Using R, we generated descriptive statistics and tested for associations with demographic variables. We also compared this study population to other previously studied populations with high ESCC incidence rates. Results: We successfully measured 247 control subjects from Malawi and found a median (IQR) serum selenium concentration of 77.3μg/L (65.9-89.5). 79 (31.9%) subjects were below the 72.2 subjects μg/L threshold of the median level of selenium We found no statistically significant associations between serum selenium concentrations and demographic characteristics including sex, education, marital status, and several risk factors for ESCC previously identified in the underlying case-control study. The serum selenium concentrations in these subjects were low and similar to previously studied regions where ESCC is common including both Bomet, Kenya and Linxian, China. Conclusion: We found low median serum selenium levels in control subjects from a hospital-based case-control study of ESCC conducted in Malawi, a region known to have high rates of ESCC. The range was similar to other populations with high incidence of ESCC. Direct linkage to disease risk will require different study designs, but our findings suggest that selenium deficiency could be a factor in the high burden of ESCC in East Africa. Citation Format: Emmanuel Uduh, Yukiko Yano, Yingxi Chen, Christian Abnet, Bongani Kaimila, Shiraz Khan. Descriptive analysis of selenium levels in a healthy Malawian subpopulation: Findings from a control study on esophageal squamous cell carcinoma (ESCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6190.