Evaluation of the Epidemiologic Efficacy of Eradicating Helicobacter pylori on Development of Gastric Cancer

Characteristic endoscopic findings in Helicobacter pylori diagnosis in clinical practice

INTRODUCTION

Helicobacter pylori is a major risk factor for gastric cancer. In addition to eradication therapy, early-phase detection of gastric cancer through screening programs using high-vision endoscopy is also widely known to reduce mortality. Although European and US guidelines recommend evaluation of atrophy and intestinal metaplasia by high-vision endoscopy and pathological findings, the guideline used in Japan - the Kyoto classification of gastritis - is based on endoscopic evaluation, and recommends the grading of risk factors. This system requires classification into three endoscopic groups: H. pylori-negative, previous H. pylori infection (inactive gastritis), and current H. pylori infection (active gastritis). Major endoscopic findings in active gastritis are diffuse redness, enlarged folds, nodularity, mucosal swelling, and sticky mucus, while those in H pylori-related gastritis - irrespective of active or inactive status - are atrophy, intestinal metaplasia, and xanthoma.

AREAS COVERED

This review describes the endoscopic characteristics of current H. pylori infection, and how characteristic endoscopic findings should be evaluated.

EXPERT OPINION

Although the correct evaluation of endoscopic findings related to H. pylori remains necessary, if findings of possible infection are observed, it is important to diagnose infection by detection methods with high sensitivity and specificity, including the stool antigen test and urea breath test.

Inflammatory response in gastrointestinal cancers: Overview of six transmembrane epithelial antigens of the prostate in pathophysiology and clinical implications

Chronic inflammation is known to increase the risk of gastrointestinal cancers (GICs), the common solid tumors worldwide. Precancerous lesions, such as chronic atrophic inflammation and ulcers, are related to inflammatory responses in vivo and likely to occur in hyperplasia and tumorigenesis. Unfortunately, due to the lack of effective therapeutic targets, the prognosis of patients with GICs is still unsatisfactory. Interestingly, it is found that six transmembrane epithelial antigens of the prostate (STEAPs), a group of metal reductases, are significantly associated with the progression of malignancies, playing a crucial role in systemic metabolic homeostasis and inflammatory responses. The structure and functions of STEAPs suggest that they are closely related to intracellular oxidative stress, responding to inflammatory reactions. Under the imbalance status of abnormal oxidative stress, STEAP members are involved in cell transformation and the development of GICs by inhibiting or activating inflammatory process. This review focuses on STEAPs in GICs along with exploring their potential molecular regulatory mechanisms, with an aim to provide a theoretical basis for diagnosis and treatment strategies for patients suffering from these types of cancers.

Estimation of gastric cancer burden attributable to Helicobacter pylori infection in Asia

BACKGROUND

Helicobacter pylori causes large burden of gastric cancer (GC) in Asia. We aimed to comprehensively quantify the burden of GC attributable to H. pylori infection in Asia.

METHODS

We searched related articles from January 1998 to December 2020 to obtain the prevalence and relative risks (or odds ratio) of GC associated with H. pylori in Asia. The burden of GC attributable to H. pylori infection was quantified by Population Attributable Fraction (PAF) and Disability-adjusted life-years (DALYs).

RESULTS

We quantified the burden of GC attributable to H. pylori infection with 415.6 thousand DALYs and 38.03% PAF through the five included Asian countries in 2019. The study found that the burden had obvious regional differences. The DALYs ranged from 298.9 thousand in China to 1.9 thousand in Malaysia, and the PAFs were between 58.00% in Japan and 30.89% in China. The average prevalence of H. pylori in the included general population was estimated to be 56.29%.

CONCLUSIONS

Helicobacter pylori poses a huge disease burden of GC to the population, and its eradication should receive attention, especially in the countries with high incidence of and mortality due to GC.

Effect of Helicobacter pylori Eradication on Gastric Cancer Prevention: Updated Report From a Randomized Controlled Trial With 26.5 Years of Follow-up

BACKGROUND & AIMS

Helicobacter pylori infection is considered as the most important risk factor in the pathogenesis of gastric cancer. This study aims to evaluate the long-term effects of H pylori eradication treatment on the incidence and mortality of gastric cancer among a high-risk population.

METHODS

This prospective, randomized, placebo-controlled trial was conducted in a high-risk area in southern China in July 1994. A total of 1630 asymptomatic, H pylori-infected individuals were randomly assigned to receive standard triple therapy for H pylori eradication (n = 817) or placebo (n = 813), and were followed up until December 2020. The primary outcome was incidence of gastric cancer. Total and cause-specific mortalities were the secondary outcomes.

RESULTS

During 26.5 years of follow-up, 21 participants (2.57%) in the treatment arm and 35 (4.31%) in the placebo arm were diagnosed with gastric cancer. Participants receiving H pylori treatment had a lower incidence of gastric cancer compared with their placebo counterparts (hazard ratio [HR], 0.57; 95% CI, 0.33-0.98). More obvious risk reduction was observed among those without premalignant gastric lesions (HR, 0.37; 95% CI, 0.15-0.95) and those without dyspepsia symptoms at baseline (HR, 0.44; 95% CI, 0.21-0.94). Furthermore, compared with 32 cases of gastric cancer observed among 527 participants with persistent H pylori infection in the placebo group, only 16 were identified in 625 subjects with successful eradication in the treatment group (HR, 0.46; 95% CI, 0.26-0.83). However, there were no statistically significant differences for any mortality end points between the 2 groups.

CONCLUSIONS

Eradication of H pylori might confer a long-term protection against gastric cancer in high-risk populations, especially for infected individuals without precancerous gastric lesions at baseline.

An Overview of Helicobacter pylori Survival Tactics in the Hostile Human Stomach Environment

Helicobacter pylori is well established as a causative agent for gastritis, peptic ulcer, and gastric cancer. Armed with various inimitable virulence factors, this Gram-negative bacterium is one of few microorganisms that is capable of circumventing the harsh environment of the stomach. The unique spiral structure, flagella, and outer membrane proteins accelerate H. pylori movement within the viscous gastric mucosal layers while facilitating its attachment to the epithelial cells. Furthermore, secretion of urease from H. pylori eases the acidic pH within the stomach, thus creating a niche for bacteria survival and replication. Upon gaining a foothold in the gastric epithelial lining, bacterial protein CagA is injected into host cells through a type IV secretion system (T4SS), which together with VacA, damage the gastric epithelial cells. H. pylori does not only establishes colonization in the stomach, but also manipulates the host immune system to permit long-term persistence. Prolonged H. pylori infection causes chronic inflammation that precedes gastric cancer. The current review provides a brief outlook on H. pylori survival tactics, bacterial-host interaction and their importance in therapeutic intervention as well as vaccine development.

Endoscopy Is Cost-Effective for Gastric Cancer Screening After Successful Helicobacter pylori Eradication

BACKGROUND

After successful Helicobacter pylori eradication, patients with gastric mucosal atrophy are at high risk of gastric cancer. Endoscopy can detect early gastric cancer with high sensitivity.

AIMS

This study aimed to assess the cost-effectiveness of annual endoscopy versus biennial endoscopy versus no screening for gastric cancer screening in patients after successful Helicobacter pylori eradication.

METHODS

We developed decision trees with Markov models for a hypothetical cohort of patients aged 50 years after successful Helicobacter pylori eradication over a lifetime horizon from a healthcare payer perspective. Main outcomes were costs, quality-adjusted life-years (QALYs), life expectancy life-years (LYs) with discounting at a fixed annual rate of 3%, and incremental cost-effectiveness ratios (ICERs).

RESULTS

In a base-case analysis, biennial endoscopy (US$4305, 19.785QALYs, 19.938LYs) was more cost-effective than annual endoscopy (US$7516, 19.808QALYs, 19.958LYs, ICER; US$135,566/QALY gained) and no screening (US$14,326, 19.704QALYs, 19.873LYs). In scenario analyses, biennial endoscopy for patients with mild-to-moderate gastric mucosal atrophy and annual endoscopy for patients with severe gastric mucosal atrophy were the most cost-effective. Cost-effectiveness was sensitive to incidence of gastric cancer and the proportion of stage I. Probabilistic sensitivity analyses using Monte Carlo simulation demonstrated that at a willingness-to-pay level of US$100,000/QALY gained, biennial endoscopy was optimal 99.9% for patients with mild-to-moderate gastric mucosal atrophy, and that annual endoscopy was optimal 98.4% for patients with severe gastric mucosal atrophy.

CONCLUSIONS

Based on cancer risk assessment of gastric mucosal atrophy and cost-effectiveness results, annual or biennial endoscopic surveillance could be established for patients after successful Helicobacter pylori eradication.

Genetic variant of cyclooxygenase-2 in gastric cancer: More inflammation and susceptibility

Gastric cancer accounts for the majority cancer-related deaths worldwide. Although various methods have considerably improved the screening, diagnosis, and treatment of gastric cancer, its incidence is still high in Asia, and the 5-year survival rate of advanced gastric cancer patients is only 10%-20%. Therefore, more effective drugs and better screening strategies are needed for reducing the incidence and mortality of gastric cancer. Cyclooxygenase-2 (COX-2) is considered to be the key inducible enzyme in prostaglandins (PGs) synthesis, which is involved in multiple pathways in the inflammatory response. For example, inflammatory cytokines stimulate innate immune responses via Toll-like receptors and nuclear factor-kappa B to induce COX-2/PGE2 pathway. In these processes, the production of an inflammatory microenvironment promotes the occurrence of gastric cancer. Epidemiological studies have also indicated that non-steroidal anti-inflammatory drugs can reduce the risk of malignant tumors of the digestive system by blocking the effect of COX-2. However, clinical use of COX-2 inhibitors to prevent or treat gastric cancer may be limited because of potential side effects, especially in the cardiovascular system. Given these side effects and low treatment efficacy, new therapeutic approaches and early screening strategies are urgently needed. Some studies have shown that genetic variation in COX-2 also play an important role in carcinogenesis. However, the genetic variation analysis in these studies is incomplete and isolated, pointing out only a few single nucleotide polymorphisms (SNPs) and the risk of gastric cancer, and no comprehensive study covering the whole gene region has been carried out. In addition, copy number variation (CNV) is not mentioned. In this review, we summarize the SNPs in the whole COX-2 gene sequence, including exons, introns, and both the 5' and 3' untranslated regions. Results suggest that COX-2 does not increase its expression through the CNV and the SNPs in COX-2 may serve as the potential marker to establish risk stratification in the general population. This review synthesizes emerging insights of COX-2 as a biomarker in multiple studies, summarizes the association between whole COX-2 sequence variation and susceptibility to gastric cancer, and discusses the future prospect of therapeutic intervention, which will be helpful for early screening and further research to find new approaches to gastric cancer treatment.

Effects of Helicobacter pylori eradication on gastric cancer incidence in the Japanese population: a systematic evidence review

BACKGROUND

In Japan, there are ongoing efforts to shift the gastric cancer prevention and control policy priorities from barium-based screening to Helicobacter pylori (H. pylori)-oriented primary prevention. A comprehensive summary of the evidence regarding the effects of H. pylori eradication on the risk of gastric cancer could inform policy decisions.

METHODS

We conducted a systematic review and meta-analysis of published studies evaluating the effectiveness of H. pylori eradication for the prevention of gastric cancer in otherwise healthy individuals (primary prevention) and early gastric cancer patients (tertiary prevention).

RESULTS

In total, 19 studies were included. Three moderate-quality observational cohort studies showed that H. pylori eradication may be associated with a decreased risk of gastric cancer in healthy asymptomatic Japanese people. There is moderate certainty regarding the effectiveness of H. pylori eradication in patients with gastrointestinal diseases, such as peptic ulcers. A meta-analysis of 10 observational studies with otherwise healthy individuals (mainly peptic ulcer patients) yielded an overall odds ratio of 0.34 (95% CI: 0.25-0.46). Regarding tertiary prevention, the overall odds ratio for developing metachronous gastric cancer was 0.42 (95% CI: 0.35-0.51) in the eradication group in a meta-analysis of nine studies involving early gastric cancer patients who underwent endoscopic resection.

CONCLUSION

H. pylori eradication is effective in preventing gastric cancer in the Japanese population, regardless of symptoms. Well-designed, large cohort studies are warranted to determine the long-term efficacy and safety of H. pylori eradication in the context of reducing the gastric cancer burden through population-based screening and treatment.

Detection of early stage gastric cancers in screening laser endoscopy using linked color imaging for patients with atrophic gastritis

BACKGROUND AND AIMS

Laser endoscopy involves blue laser imaging in bright mode (BLI-bright). Linked color imaging (LCI) is superior to white light imaging (WLI) for detecting gastric cancers. This study aimed to detect gastric cancers on screening endoscopy using not only WLI but also BLI-bright and LCI in patients with atrophic gastritis.

PATIENTS AND METHODS

A total of 500 patients with atrophic gastritis undergoing screening esophagogastroduodenoscopy were included. The gastric lumen was observed in the WLI mode, followed by the LCI and BLI-bright modes. When gastric neoplasms were suspected, the mode was changed to WLI, and we sprayed indigo carmine. Finally, biopsy specimens were taken for those lesions and pathological diagnosis was made. We compared the size, morphology, and color of gastric neoplasms found by the first WLI mode and those detected by only the LCI mode or BLI-bright mode.

RESULTS

We detected 16 gastric neoplasms (3.2%), of which 13 were early gastric cancers (EGCs) and three were gastric adenomas. Ten EGCs and two gastric adenomas (75%) were detected by the first WLI mode; three EGCs and one gastric adenoma (25%) were missed by the first WLI mode and were detected by the LCI mode or BLI-bright mode. All were less than 1 cm in diameter and were reddish. Mean diameter of the lesions was significantly less for LCI-detected or BLI-bright-detected lesions than for WLI-detected lesions (7.8 vs 21.2 mm).

CONCLUSIONS

Laser endoscopy is useful for detecting EGCs by LCI for patients with atrophic gastritis.

Bile reflux is an independent risk factor for precancerous gastric lesions and gastric cancer: An observational cross-sectional study

OBJECTIVE

To identify whether bile reflux on endoscopy and other related variables are risk factors for precancerous gastric lesions and gastric cancer (GC).

METHODS

A multicenter, cross-sectional and observational study was conducted in five centers in China from June to October 2019, 1162 patients were recruited and divided into the chronic gastritis (CG), the precancerous lesion (low-grade intraepithelial neoplasia and intestinal metaplasia), and GC groups (including high-grade intraepithelial neoplasia). All participants underwent detailed interviews, endoscopy and biopsy, and completed questionnaires. Odds ratio and 95% confidence interval were calculated with multivariate logistic regression models with or without adjustment for Helicobacter pylori infection.

RESULTS

We recruited 668 patients with CG, 411 with precancerous lesions and 83 with GC. By comparing the CG and precancerous lesion groups, independent risk factors for cancerous gastric lesions were the grade of bile reflux, patient's age, dietary habits and family history of GC. Similar results were obtained when comparing the CG and GC groups. In addition, bile reflux was confirmed as an independent risk factor for progression from precancerous lesions to cancer.

CONCLUSIONS

Bile reflux on endoscopy as well as age, dietary habits and a family history of GC were independent risk factors for the development of precancerous gastric lesions and GC.