Timing of H. pylori diagnosis may limit gastric cancer prevention

Most gastric cancers develop within a short time after Helicobacter pylori diagnosis, according to a retrospective cohort study published in Clinical Gastroenterology and Hepatology, with neither treatment nor eradication — previously shown to reduce risk — lowering short-term cancer incidence.

 

"Symptom-based testing identifies infection too late for effective cancer prevention. While eradication may reduce GC [gastric cancer] risk, this benefit likely requires early detection and adequate follow-up," noted Will Takakura, MD, of Kaiser Permanente Southern California, Panorama City, and colleagues.

 

 

The investigators focused on 60,503 adults with positive H. pylori stool antigen tests from Kaiser Permanente Southern California, all with no history of gastric cancer at baseline. The cohort was 62.9% female with a median age of 49.1 years and was predominantly Hispanic (65.3%).

 

Patients were grouped by H. pylori treatment (treated vs untreated) and eradication (eradicated vs unknown vs not eradicated) status, with eradication defined by a subsequent negative test and treatment defined as filling a standard antibiotic regimen within 90 days of diagnosis. Gastric cancer cases — excluding cardia tumors — were identified by a validated registry.

 

The study assessed (1) gastric cancer prevalence at H. pylori diagnosis (defined as cancer within one year); and (2) the risk of developing new cancers after diagnosis, evaluating the impact of treatment and eradication with follow-up starting one-year post-diagnosis.

 

Cox proportional hazard models (adjusted for age, race/ethnicity, and family history, with mortality as a competing risk) estimated associations with treatment and eradication. Eradication was modeled as time-varying and treatment as fixed. A subgroup analysis evaluated the impact of delayed eradication.

 

 

In the entire cohort, 173 gastric cancer cases were diagnosed, of which 133 (76.9%) occurred within one year of H. pylori diagnosis and were thus considered prevalent.

After excluding prevalent gastric cancer cases, the effect of H. pylori treatment and eradication was assessed in 49,979 patients (median age = 49.5 years; 63.6% female).

 

During a median follow-up of 2.6 years, 40 patients developed gastric cancer, corresponding to an incidence rate of 20.5 per 100,000 person-years. Median time to gastric cancer was 1.8 years, during which 43,216 (86.8%) received H. pylori treatment; overall, 24,263 (48.7%) achieved eradication, 2,160 (4.3%) were not eradicated, and 23,374 (46.9%) had unknown eradication status. Gastric cancer risk did not appear to significantly differ for treated patients (hazard ratio [HR] = 0.90), those with eradicated infection (HR = 1.45), or with unknown eradication status (HR = 0.56).

 

The researchers, noting the short interval between H. pylori and gastric cancer diagnoses, performed a subgroup analysis of 24,263 patients with confirmed eradication — 26 of whom developed gastric cancer — to evaluate the impact of time to eradication. Patients with gastric cancer had a median eradication time of 1.12 years, whereas those without had 0.35 years. Delays in eradication were found to be linked to higher risk of gastric cancer (HR = 1.12/year).

 

“In this large, racially and ethnically diverse cohort from an integrated health care system in Southern California, we found that a large proportion of [gastric cancer] were prevalent during [H. pylori] diagnosis. In addition, neither treatment nor eradication appeared to reduce the risk of [gastric cancer], although a delay in [H. pylori] eradication appeared to increase the risk,” the researchers noted. “Our findings support recent guideline changes recommending proactive screening and treatment for [H. pylori] in high-risk populations and highlight the need for more comprehensive, upstream approaches to [gastric cancer] prevention in the United States.”