A Case-Control Study to Evaluate the Etiology of Esophageal Cancer in Tanzania

Abstract

Abstract 75 Objective: East Africa has been previously reported as a geographic area with a disproportionately high incidence of squamous cell esophageal cancer (EC). In the setting of an apparent geographic cluster, we sought to identify specific etiologic factors contributing to the high incidence of EC in Tanzania (TZ). Methods: We performed a case-control study to examine possible associations between EC and selected environmental, dietary, and lifestyle factors. Newly diagnosed EC cases were recruited at Muhimbili National Hospital and Ocean Road Cancer Institute during 2014-2015. Hospital controls were identified from patients with non-malignant conditions and matched 1:1 for gender and age ±10 years. The study team conducted in-person interviews. A matched case-control analysis used McNemar’s test with a Mantel-Haenszel estimate for odds ratios (OR). Results: 375 cases and 375 controls were enrolled. 71% of cases and controls were male. Median age was 58 years (range 30-91) for cases and 55 years (range 31-88) for controls. Among cases with a confirmed pathologic diagnosis, squamous cell carcinoma was the most common histology (85%). Liquor consumption (OR 1.84, 95% CI: 1.05-3.22, p=0.04), burning firewood (OR 2.66, 95% CI: 1.88-3.76, p<0.001), use of kerosene (OR 3.29, 95% CI: 2.36-4.59, p<0.001), and use of surface water as a primary source of drinking water (OR 2.3, 95% CI: 1.41-3.76, p=0.001) were associated with increased risk of EC. Running water, gas, and electric utilities in the household were protective. Conclusion: Alcohol consumption, firewood and kerosene use as fuel, and surface water consumption merit further investigation as potential etiologic factors contributing to high EC incidence in TZ. Future research will include conducting multivariate analysis with these and other potential risk factors and a genome-wide analysis study using DNA extracted from saliva specimens obtained from cases and controls. Funding: Research support provided by the National Cancer Institute, National Institutes of Health Contract No. HH5N261200800001E. AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST: Elia Mmbaga No relationship to disclose Katrina Deardorff No relationship to disclose Beatrice Mushi No relationship to disclose Li Zhang No relationship to disclose William Mgisha No relationship to disclose Aparna Parikh Employment: Genentech Stock or Other Ownership: Genentech Travel, Accommodations, Expenses: Genentech Robert A. Hiatt No relationship to disclose Julius Mwaiselage No relationship to disclose Katherine Van Loon Consulting or Advisory Role: Bayer Company: OncoPlex Diagnostics