Individuals who are racial or ethnic minorities and individuals who are smokers experience significantly higher risks for gastric cancer following a diagnosis of Helicobacter pylori (H pylori) infection, according to research published in Gastroenterology.

H pylori infection is the most well-known risk factor for gastric cancer. Investigators conducted a retrospective cohort study aimed at identifying the incidence of non-proximal gastric adenocarcinoma following H pylori infection. Additional aims included defining how demographics, environmental factors, and infection treatment modality affect the incidence of gastric cancer.

In total, 371,813 patients with H pylori were identified: 26,873 via endoscopic pathology, 11,262 via stool antigen, 400 via urea breath test, 266,216 via prescription of an eradication regimen, and 67,062 with administrative codes. Within the overall cohort, 0.54% of patients developed gastric adenocarcinoma over a median follow-up of 7.4 years. These patients were most likely to be older black men and to have a history of smoking. Median age at cancer diagnosis was 69 years. Moreover, the patients who developed cancer were more likely to have died (67.7% vs 37.2%).

Among patients with a positive diagnostic test, 74.8% were prescribed an eradication regimen; 20.8% then underwent retesting. Among those, the infection was successfully eradicated in 90.9%.

Multivariable competing-risk models identified several factors associated with incident diagnosis, including the H pylori diagnosis method. Patients diagnosed based only on the International Classification of Diseases code with a positive serum antibody in the adjacent 90 days were at the lowest risk (sub-hazard ratio [SHR] 0.75; 95% CI, 0.62-0.90). Additional factors associated with future gastric adenocarcinoma included each 5-year increase in age at H pylori diagnosis (SHR 1.13; 95% CI, 1.11-1.15), being black (SHR 2.00; 95% CI, 1.80-2.22), and Asian race or Hispanic ethnicity (SHR 2.52 [95% CI, 1.64-3.89] and 1.59 [95% CI, 1.34-1.87]), respectively). Smoking history was also associated with future gastric adenocarcinoma (SHR 1.38; 95% CI, 1.25-1.52).

Within this same sub-population, H pylori treatment was not associated with subsequent development of gastric adenocarcinoma (SHR 1.16; 95% CI, 0.74-1.83). Patients with confirmed H pylori who underwent eradication testing experienced a significantly lower risk for gastric adenocarcinoma (SHR 0.24; 95% CI, 0.15-0.41), although age, race, ethnicity, and tobacco history were all still associated with cancer development.

Finally, sensitivity analyses demonstrated that gastric adenocarcinoma incidence following H pylori diagnosis at 5, 10, and 20 years was 0.19%, 0.33%, and 0.49%, respectively, excluding cancers that developed within 6 months of treatment. After excluding cancers that developed within 12 months, these incidences were 0.24%, 0.38%, and 0.53%, respectively.

Study limitations included the retrospective nature of the research, inherent selection bias, a lack of generalizability due to use of a cohort made up of >90% men, and the inability to identify potential confounders.

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“Future studies should focus on consideration of screening of high-risk persons, identification of what host and [H pylori] factors predispose to increased risk, quality measures to ensure appropriate diagnosis of [H pylori] infection, and resistance patterns and efficacy treatment of [H pylori] infection,” the researchers concluded.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Kumar S, Metz DC, Ellenberg S, Kaplan DE, Goldberg DS. Risk factors and incidence of gastric cancer after detection of Helicobacter pylori infection: A large cohort study [published online October 22, 2019]. Gastroenterology. doi: 10.1053/j.gastro.2019.10.019