Gastric cancer in Zambian adults: a prospective case-control study that assessed dietary intake and antioxidant status by using urinary isoprostane excretion.

BACKGROUND: Gastric cancer is increasingly recognized in Zambia. Although nutritional factors contribute to gastric cancer risk, their effect in Zambia is unknown. OBJECTIVE: The objective was to investigate the association between intake of dietary antioxidants, urinary 8-iso prostaglandin F2α (8-iso PGF2α) as a marker of oxidative stress, and gastric cancer. DESIGN: This was a case-control study at the University Teaching Hospital in Zambia. Gastric cancer cases were compared with age- and sex-matched controls. Urine 8-iso PGF2α was measured primarily by ELISA, and by gas chromatography-mass spectrometry in a subset, expressed as a ratio to creatinine. Blood was collected for Helicobacter pylori, HIV serology, gastrin-17, and pepsinogen 1 and 2 concentrations. Clinical and dietary data were collected by using questionnaires. Food items were broadly classified into 7 major categories (fruit, vegetables, fish, meat, insects, cereals, and starches). RESULTS: Fifty cases with gastric cancer (mean age: 61 y; n = 31 males) and 90 controls (mean age: 54 y; n = 41 males) were enrolled. Median urinary 8-iso PGF2α excretion was higher in cases (0.014; IQR: 0.008-0.021) than in controls (0.011; IQR: 0.006-0.018; P = 0.039). On univariate analysis, habitual fruit intake was lower in cases than in controls during the dry season (P = 0.02). On multivariate analysis, smoking (OR: 7.22; IQR: 1.38-37.9) and gastric atrophy (OR: 2.43; IQR: 1.12-5.13) were independently associated with cancer, and higher fruit intake was protective (OR: 0.44; IQR: 0.20-0.95). Isoprostane excretion was inversely correlated with total fruit intake (ρ = -0.23; n = 140; P = 0.006). CONCLUSION: Urinary 8-iso PGF2α excretion was associated with the risk of gastric cancer, as were smoking and gastric atrophy, but increased fruit intake conferred protection. This trial was registered at www.pactr.org as ISRCTN52971746.