Dose-response association between cigarette smoking and gastric cancer risk: a systematic review and meta-analysis

Chronic cigarette smoke exposure masks pathological features of Helicobacter pylori infection while promoting tumor initiation

Gastric cancer is the fifth most common cancer and the fifth leading cause of cancer deaths worldwide. Chronic infection by the bacterium Helicobacter pylori is the most prominent gastric cancer risk factor, but only 1-3% of infected individuals will develop gastric cancer. Cigarette smoking is another independent gastric cancer risk factor, and H. pylori- infected smokers are at a 2-11-fold increased risk of gastric cancer development, but the direct impacts of cigarette smoke on H. pylori pathogenesis remain unknown. In this study, male C57BL/6 mice were infected with H. pylori and began smoking within one week of infection. The mice were exposed to cigarette smoke (CS) five days/week for 8 weeks. CS exposure had no notable impact on gross gastric morphology or inflammatory status compared to filtered-air (FA) exposed controls in mock-infected mice. However, CS exposure significantly blunted H. pylori- induced gastric inflammatory responses, reducing gastric atrophy and pyloric metaplasia development. Despite blunting these classic pathological features of H. pylori infection, CS exposures increased DNA damage within the gastric epithelial cells and accelerated H. pylori- induced dysplasia onset in the INS-GAS gastric cancer model. These data suggest that cigarette smoking may clinically silence classic clinical symptoms of H. pylori infection but enhance the accumulation of mutations and accelerate gastric cancer initiation.

The Impact of Tobacco Smoking and Alcohol Consumption on the Development of Gastric Cancers

Chronic infection of Helicobacter pylori is considered the principal cause of gastric cancers, but evidence has accumulated regarding the impact of tobacco smoking and alcohol consumption on the development of gastric cancers. Several possible mechanisms, including the activation of nicotinic acetylcholine receptors, have been proposed for smoking-induced gastric carcinogenesis. On the other hand, local acetaldehyde exposure and ethanol-induced mucosal inflammation have been proposed as the mechanisms involved in the development of gastric cancers in heavy alcohol drinkers. In addition, genetic polymorphisms are also considered to play a pivotal role in smoking-related and alcohol-related gastric carcinogenesis. In this review, we will discuss the molecular mechanisms involved in the development of gastric cancers in relation to tobacco smoking and alcohol consumption.

Stomach Cancer Prediction Model (SCoPM): An approach to risk stratification in a diverse U.S. population

BACKGROUND AND AIMS

Population-based screening for gastric cancer (GC) in low prevalence nations is not recommended. The objective of this study was to develop a risk-prediction model to identify high-risk patients who could potentially benefit from targeted screening in a racial/ethnically diverse regional US population.

METHODS

We performed a retrospective cohort study from Kaiser Permanente Southern California from January 2008-June 2018 among individuals age ≥50 years. Patients with prior GC or follow-up <30 days were excluded. Censoring occurred at GC, death, age 85 years, disenrollment, end of 5-year follow-up, or study conclusion. Cross-validated LASSO regression models were developed to identify the strongest of 20 candidate predictors (clinical, demographic, and laboratory parameters). Records from 12 of the medical service areas were used for training/initial validation while records from a separate medical service area were used for testing.

RESULTS

1,844,643 individuals formed the study cohort (1,555,392 training and validation, 289,251 testing). Mean age was 61.9 years with 53.3% female. GC incidence was 2.1 (95% CI 2.0-2.2) cases per 10,000 person-years (pyr). Higher incidence was seen with family history: 4.8/10,000 pyr, history of gastric ulcer: 5.3/10,000 pyr, H. pylori: 3.6/10,000 pyr and anemia: 5.3/10,000 pyr. The final model included age, gender, race/ethnicity, smoking, proton-pump inhibitor, family history of gastric cancer, history of gastric ulcer, H. pylori infection, and baseline hemoglobin. The means and standard deviations (SD) of c-index in validation and testing datasets were 0.75 (SD 0.03) and 0.76 (SD 0.02), respectively.

CONCLUSIONS

This prediction model may serve as an aid for pre-endoscopic assessment of GC risk for identification of a high-risk population that could benefit from targeted screening.

Cancer mortality predictions for 2024 in selected Asian countries and Australia with focus on stomach cancer

INTRODUCTION

We estimated cancer mortality figures in five major Asian countries and Australia for 2024, focusing on stomach cancer, a leading cause of cancer-related deaths in Eastern Asia.

METHODS

We computed country- and sex-specific annual age-standardized rates (ASRs) for total cancers and the 10 most common cancer sites, using WHO and the United Nations Population Division databases from 1970 to 2021 or the latest available year. We predicted figures for 2024 and estimated the number of avoided cancer deaths in 1994-2024.

RESULTS

All cancers combined ASR declined between 2015-2019 and 2024 across considered countries and sexes. In 2024, the lowest predicted male rate is in the Philippines (75.0/100 000) and the highest in Australia (94.2/100 000). The Republic of Korea is predicted to have the lowest female ASR (42.1/100 000) while the Philippines the highest (74.5/100 000). Over the last three decades, 121 300 deaths were estimated to be avoided in Hong Kong SAR, 69 500 in Israel, 1 246 300 in Japan, 653 300 in the Republic of Korea, 303 300 in Australia, and 89 700 among Philippine men. Mortality from stomach cancer has been decreasing since 1970 in all considered countries and both sexes. Significant decreases are at all age groups Male rates remain, however, high in Japan (8.7/100 000) and the Republic of Korea (6.2/100 000).

CONCLUSION

Declining cancer mortality is predicted in the considered countries, notably reducing stomach cancer burden. Stomach cancer, however, remains a major public health issue in East Asia.