Background & aims: Nearly all studies of gastric adenocarcinoma in the United States have relied on national cancer databases, which do not include data on Helicobacter pylori infection, the most well-known risk factor for gastric cancer. We collected data from a large cohort of patients in the United States to calculate the incidence of and risk factors for nonproximal gastric adenocarcinomas after detection of H pylori. Secondary aims included identifying how treatment and eradication affect cancer risk.
Methods: We performed a retrospective cohort study, collecting data from the Veterans Health Administration on 371,813 patients (median age 62 years; 92.3% male) who received a diagnosis of H pylori infection from January 1, 1994, through December 31, 2018. The primary outcome was a diagnosis of distal gastric adenocarcinoma 30 days or more after detection of H pylori infection. We performed a time to event with competing risk analysis (with death before cancer as a competing risk).
Results: The cumulative incidence of cancer at 5, 10, and 20 years after detection of H pylori infection was 0.37%, 0.5%, and 0.65%, respectively. Factors associated with cancer included older age at time of detection of H pylori infection (subhazard ratio [SHR], 1.13; 95% confidence interval [CI], 1.11-1.15; P < .001), black/African American race (SHR, 2.00; 95% CI, 1.80-2.22), Asian race (SHR, 2.52; 95% CI, 1.64-3.89) (P < .001 for race), Hispanic or Latino ethnicity (SHR, 1.59; 95% CI, 1.34-1.87; P < .001), and history of smoking (SHR, 1.38; 95% CI, 1.25-1.52; P < .001). Women had decreased risk of gastric adenocarcinoma compared with men (SHR, 0.52; 95% CI, 0.40-0.68; P < .001); patients whose H pylori infection was detected based on serum antibody positivity also had a reduced risk of cancer (SHR 0.74; 95% CI, 0.54-1.04; P = .04). Patients who received treatment for their H pylori infection still had an increased risk of gastric cancer (SHR, 1.16; 95% CI, 0.74-1.83; P = .51) but confirmed H pylori eradication after treatment reduced risk of gastric cancer (SHR, 0.24; 95% CI, 0.15-0.41; P < .001).
Conclusions: In a study of 371,813 veterans with a diagnosis of H pylori infection, we found significantly higher risks of gastric cancer in racial and ethnic minorities and smokers. Treatment of H pylori infection decreased risk only if eradication was successful. Studies are needed on the effects of screening high-risk persons and to identify quality measures for diagnosis, resistance patterns, and treatment efficacy.
Keywords: Antibacterial Therapy; Microbe; Screening; Stomach Cancer.
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