Factors contributing to the underestimation of Helicobacter pylori-associated gastric cancer risk in a high-prevalence population

The protective effect of dietary folate intake on gastric cancer is modified by alcohol consumption: A pooled analysis of the StoP Consortium

Dietary folate intake has been identified as a potentially modifiable factor of gastric cancer (GC) risk, although the evidence is still inconsistent. We evaluate the association between dietary folate intake and the risk of GC as well as the potential modification effect of alcohol consumption. We pooled data for 2829 histologically confirmed GC cases and 8141 controls from 11 case-control studies from the international Stomach Cancer Pooling Consortium. Dietary folate intake was estimated using food frequency questionnaires. We used linear mixed models with random intercepts for each study to calculate adjusted odds ratios (OR) and 95% confidence interval (CI). Higher folate intake was associated with a lower risk of GC, although this association was not observed among participants who consumed >2.0 alcoholic drinks/day. The OR for the highest quartile of folate intake, compared with the lowest quartile, was 0.78 (95% CI, 0.67-0.90, P-trend = 0.0002). The OR per each quartile increment was 0.92 (95% CI, 0.87-0.96) and, per every 100 μg/day of folate intake, was 0.89 (95% CI, 0.84-0.95). There was a significant interaction between folate intake and alcohol consumption (P-interaction = 0.02). The lower risk of GC associated with higher folate intake was not observed in participants who consumed >2.0 drinks per day, ORQ4v Q1 = 1.15 (95% CI, 0.85-1.56), and the OR100 μg/day = 1.02 (95% CI, 0.92-1.15). Our study supports a beneficial effect of folate intake on GC risk, although the consumption of >2.0 alcoholic drinks/day counteracts this beneficial effect.

"True" Helicobacter pylori infection and non-cardia gastric cancer: A pooled analysis within the Stomach Cancer Pooling (StoP) Project

BACKGROUND

Helicobacter pylori is the most important risk factor for non-cardia gastric cancer (NCGC); however, the magnitude of the association varies across epidemiological studies. This study aimed to quantify the association between H. pylori infection and NCGC, using different criteria to define infection status.

METHODS

A pooled analysis of individual-level H. pylori serology data from eight international studies (1325 NCGC and 3121 controls) from the Stomach Cancer Pooling (StoP) Consortium was performed. Cases and controls with a negative H. pylori infection status were reclassified as positive considering the presence of anti-Cag A antibodies, gastric atrophy, or advanced stage at diagnosis, as available and applicable. A two-stage approach was used to pool study-specific adjusted odds ratios (OR), and 95% confidence intervals (95% CI). A meta-analysis of published prospective studies assessing H. pylori seropositivity in NCGCs was conducted.

RESULTS

The OR for the association between serology-defined H. pylori and NCGC was 1.45 (95% CI: 0.87-2.42), which increased to 4.79 (95% CI: 2.39-9.60) following the reclassification of negative H. pylori infection. The results were consistent across strata of sociodemographic characteristics, clinical features and lifestyle factors, though significant differences were observed according to geographic region-a stronger association in Asian studies. The pooled risk estimates from the literature were 3.01 (95% CI: 2.22-4.07) for ELISA or EIA and 9.22 (95% CI: 3.12-27.21) for immunoblot or multiplex serology.

CONCLUSION

The NCGC risk estimate from StoP based on the reclassification of H. pylori seronegative individuals is consistent with the risk estimates obtained from the literature. Our classification algorithm may be useful for future studies.

Prevalence of Helicobacter pylori in Non-Cardia Gastric Cancer in China: A Systematic Review and Meta-Analysis

Non-cardia gastric cancer was significantly associated with Helicobacter pylori (H. pylori) infection. Reducing H. pylori prevalence was an important prevention strategy for non-cardia gastric cancer. However, national-level data on the H. pylori prevalence in non-cardia gastric cancer were limited in China. Therefore, we conducted this study to estimate the pooled prevalence of H. pylori in non-cardia gastric cancer in China. We searched PubMed, Embase, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wan Fang, and VIP Database for Chinese Technical Periodicals for studies reporting H. pylori prevalence in non-cardia gastric cancer in China which were published before September 1, 2021. Pooled prevalence was calculated using a random-effect model. Subgroup analysis and meta-regression were used to explore the potential sources of heterogeneity. Egger’s test and funnel plot were used to assess publication bias. A total number of 55 studies with 5324 cases of non-cardia gastric cancer were included in this study. The pooled prevalence of H. pylori in non-cardia gastric cancer in China was 66.5% (95%CI: 62%-71%, I²=93.8%, P<0.0001). In subgroup analysis, a significant difference in the prevalence of H. pylori in non-cardia gastric cancer was noted when stratified by geographic region of China (P=0.0112). The highest H. pylori prevalence (78.9%, 95%CI: 69.9%-87.8%) was noted in Northwest China and the lowest (53.1%, 95%CI: 38.9%-67.3%) was in North China. In meta-regression, a significant association between H. pylori prevalence and geographic region was found, while type of sample, H. pylori testing method, diagnosis period, detection timing, type of study design, quality grade, publication year, and sample size were not associated with the prevalence of H. pylori in non-cardia gastric cancer (P>0.05). A large proportion of non-cardia gastric cancers were associated with H. pylori infection in China, emphasizing the possible benefits of H. pylori eradication for the prevention and control of non-cardia gastric cancer.

Identifying the profile of Helicobacter pylori negative gastric cancers: a case only analysis within the Stomach cancer Pooling (StoP) Project

BACKGROUND

The prevalence of Helicobacter pylori negative gastric cancer (HpNGC) can be as low as 1%, when infection is assessed using more sensitive tests or considering the presence of gastric atrophy. HpNGC may share a high-risk profile contributing to the occurrence of cancer in the absence of infection. We estimated the proportion of HpNGC, using different criteria to define infection status, and compared HpNGC and positive cases regarding gastric cancer risk factors.

METHODS

Cases from 12 studies from the Stomach cancer Pooling (StoP) Project providing data on H. pylori infection status determined by serological test were included. HpNGC was reclassified as positive (eight studies) when cases presented CagA markers (four studies), gastric atrophy (six studies), or advanced stage at diagnosis (three studies), and were compared with positive cases. A two-stage approach (random-effects models) was used to pool study-specific prevalence and adjusted odds ratios (ORs).

RESULTS

Among non-cardia cases, the pooled prevalence of HpNGC was 22.4% (n=166/853) and decreased to 7.0% (n=55) when considering CagA status; estimates for all criteria were 21.8% (n=276/1325) and 6.6% (n=97), respectively. HpNGC had a family history of gastric cancer more often (OR=2.18, 95% confidence interval [CI]:1.03-4.61) and were current smokers (OR=2.16, 95%CI:0.52-9.02).

CONCLUSION

This study found a low prevalence of HpNGC, who are more likely to have a family history of gastric cancer in first-degree relatives.

IMPACT

Our results support that H. pylori infection is present in most non-cardia gastric cancers, and suggest that HpNGC may have distinct patterns of exposure to other risk factors.

Exploring the interactions between Helicobacter pylori (Hp) infection and other risk factors of gastric cancer: A pooled analysis in the Stomach cancer Pooling (StoP) Project

Helicobacter pylori (Hp) is crucial in gastric carcinogenesis, but infection alone is not a sufficient cause, and the interaction between Hp infection and other risk factors has not been adequately studied. We conducted a pooled analysis of seven case-control studies from the Stomach cancer Pooling (StoP) Project, comprising 1377 cases and 2470 controls, to explore the interaction among Hp infection and tobacco smoking, alcohol drinking, socioeconomic status (SES) and dietary salt intake on the risk of gastric cancer. We estimated summary odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) by multivariate unconditional logistic regression. The analysis showed no consistent interaction between Hp infection and cigarette smoking, while interaction was more than multiplicative for alcohol drinking (OR = 1.38, 95% CI: 1.07-1.77, P-interaction 0.02) and high intake of salt (OR = 2.62, 95% CI: 1.88-3.65, P-interaction = 0.04). The interaction with SES followed the multiplicative model (P = 0.49), resulting in a weakening among infected individuals of the protective effect of high SES among observed Hp-negative individuals. The interactions found were more pronounced in subjects with history of peptic ulcer. The interactions with Hp infection were stronger for cigarette smoking and dietary salt in the case of noncardia cancer, and for alcohol and SES in the case of cardia cancer. No differences were found when stratifying for histologic type. This large-scale study aimed to quantify the interaction between Hp infection and other modifiable risk factors of gastric cancer revealed that the benefit of combined Hp eradication and lifestyle modification on gastric cancer prevention may be larger than commonly appreciated.

Associations Between Gastric Cancer Risk and Virus Infection Other Than Epstein-Barr Virus: A Systematic Review and Meta-analysis Based on Epidemiological Studies

INTRODUCTION

Besides Helicobacter pylori and Epstein-Barr virus, other viruses might play potential roles in gastric carcinogenesis. This systematic review and meta-analysis was conducted to compare the prevalence of the viruses between gastric cancer (GC) and any controls.

METHODS

Comprehensive literature was searched up to January 25, 2019, and search was updated on April 6, 2020. The studies that compared the prevalence of viruses other than Epstein-Barr virus between GC and healthy or nonmalignant controls were eligible. Stata 12.0 software was used for heterogeneity tests and meta-analyses. Meanwhile, subgroup analysis, sensitivity analysis, and publication bias evaluation were performed where applicable. The power (1-β) was estimated by the PASS 11 software for each individual study.

RESULTS

A total of 41 eligible studies were included, concerning 11 kinds of viruses. Prevalence were significantly higher in GC for hepatitis B virus (odds ratio [OR] = 1.39, 95% confidence interval [CI] 1.11-1.75), human cytomegalovirus (OR = 2.25, 95% CI 1.14-4.43), human papillomavirus (HPV) (OR = 1.63, 95% CI 1.05-2.54), and John Cunningham virus (OR = 2.52, 95% CI 1.26-5.04). In subgroup analyses, HPV-16 infection was significantly associated with GC (OR = 2.42, 95% CI 1.00-5.83).

DISCUSSION

This study demonstrated that hepatitis B virus, human cytomegalovirus, HPV, and John Cunningham virus were more prevalent in GC. However, the causal relationship between their infection and risk of GC remains inconclusive, and further investigations are required.

Associations between hepatitis B virus exposure and the risk of extrahepatic digestive system cancers: A hospital-based, case-control study (SIGES)

OBJECTIVES

This case-control study was aimed to investigate associations between HBV infection and extrahepatic digestive system cancers.

METHODS

The patients of gastric, small intestinal, colonic, rectal, anal, biliary tract, and pancreatic cancers were retrospectively collected between 2016.5 and 2017.12. Simultaneously, the healthy controls were collected from the health check-up registry, and cancer-free status was confirmed based on medical records. Propensity score matching was performed to reduce bias. Multinomial logit model and conditional logistic regression model were used to assess the risk of individual cancer according to HBV serological markers and classifications.

RESULTS

Totally, 4748 patients involving seven cancers, and 57,499 controls were included. After matching, HBsAg was associated with increased risk of gastric cancer (aOR = 1.39, 95% CI: 1.05-1.85), and anti-HBs served as a protective factor for gastric (aOR = 0.72, 95% CI: 0.61-0.85), colonic (aOR = 0.73, 95% CI: 0.60-0.89), rectal (aOR = 0.73, 95% CI: 0.63-0.85), and pancreatic (aOR = 0.58, 95% CI: 0.42-0.82) cancers. Compared to subgroups with non-infection and vaccination status, inactive HBsAg carriers and active HBV infection subgroup were correlated with gastric carcinogenesis (aOR = 1.41, 95% CI: 1.03-1.93). However, no clear association was found between HBV infection and other cancers.

CONCLUSIONS

HBV infection was potentially associated with an increased risk of gastric cancer. The development mechanism of HBV-associated gastric cancer needs to investigate further.

Cancers attributable to infections in Canada

Infections are estimated to cause approximately 15% of the world's cancers with large geographic variations. Yet, Canadian estimates for specific cancer-causing infections are not available. To estimate the number of infection-associated cancers diagnosed among Canadian adults in 2015, we calculated population attributable risks (PARs) and the number of attributable cases for seven carcinogenic infections and their 20 associated cancers. A systematic literature search was performed for each infection to obtain data on infection prevalence in the population and the relative risk or odds ratio associated with the cancer it causes. When mechanistic evidence suggested that detection of a given infection within cancer tissue was sufficient to attribute the cancer to the infection, prevalence among cancer cases was used to approximate the PAR. Data from 61 studies formed the basis of our analyses. The estimated number of infection-attributable cancer cases for 2015 was: 3828 for human papillomavirus (HPV), 2052 for Helicobacter pylori, 578 for Epstein-Barr virus, 509 for hepatitis B and C viruses (HBV, HCV), 100 for human herpesvirus type 8, and 30 cases for human T-cell lymphotropic virus type 1. These seven infections were responsible for 3.7% of cancers diagnosed among Canadian adults in 2015; 3.5% among men and 4.0% among women. The infections with the highest number of attributable cases are largely preventable or treatable through vaccination (HBV and HPV), antibiotic therapy (H. pylori), or a combination of interventions (HCV), thereby representing an important target for reducing the infection-caused cancer burden among Canadians.

Sex differences in the prevalence of Helicobacter pylori infection: an individual participant data pooled analysis (StoP Project)

BACKGROUND

Helicobacter pylori (H. pylori) infection is more frequent among men, though the magnitude of the association might be inaccurate due to potential misclassification of lifetime infection and publication bias. Moreover, infection is common, and most studies are cross-sectional. Thus, prevalence ratios (PRs) may be easier to interpret than odds ratios (ORs).

AIM

The aim of this study was to quantify the association between sex and H. pylori infection using controls from 14 studies from the Stomach Cancer Pooling (StoP) Project.

PARTICIPANTS AND METHODS

H. pylori infection was defined based on IgG serum antibody titers or multiplex serology. Participants were also classified as infected if gastric atrophy was present, based on histological examination or serum pepsinogen (PG) levels (PG I≤70 and PG I/II ratio≤3). Summary ORs and PRs, adjusted for age, social class and smoking, and corresponding 95% confidence intervals (CIs), were estimated through random-effects meta-analysis.

RESULTS

Men had significantly higher OR (OR: 1.33, 95% CI: 1.04-1.70) and PR (PR: 1.05, 95% CI: 1.00-1.10) of infection, with stronger associations among hospital-based or older controls. Results were similar when considering the presence of gastric atrophy to define infection status, particularly among participants older than 65 years.

CONCLUSION

This collaborative pooled-analysis supports an independent effect of sex on the prevalence of H. pylori infection, while minimizing misclassification of lifetime infection status and publication bias.

Helicobacter pylori Infection and Risk of Gastric Cancer in Korea: A Quantitative Systematic Review

Objectives:

In the context of the global decrease in mortality due to gastric cancer, previous studies have reported that the effect of chronic Helicobacter pylori (H. pylori) infection on the incidence of gastric cancer varies among regions. This systematic review was conducted to investigate H. pylori as a risk factor for gastric cancer in Korea, where the incidence of gastric cancer is among the highest in the world.

Methods:

A search strategy was established to identify articles published in Korean as well as in English. Ultimately, we included observational studies conducted among Korean patients that designed with an age-matched and sex-matched control group that reported the odds ratio associated with H. pylori. Gastric cancer cases were subdivided into overall (OGC), cardia (CGC), non-cardia (NGC), early (EGC), advanced, intestinal (IGC), and diffuse forms of gastric cancer. Summary odds ratios (SORs) with 95% confidence intervals (CIs) were calculated in the meta-analysis using a random-effect model.

Results:

Eleven case-control studies were ultimately selected. H. pylori was associated with an SOR of 1.81 (95% CI, 1.29 to 2.54) for OGC. Additionally, statistically significant risks were observed for CGC, NGC, EGC, and IGC.

Conclusions:

Chronic H. pylori infection was found to raise the risk of gastric cancer among Koreans, with the highest risk observed for CGC and EGC (SOR=2.88 for both). Follow-up clinical epidemiologic studies are needed to assess the effects of current treatments aimed at eradicating H. pylori infections.

Global burden of gastric cancer attributable to Helicobacter pylori

We previously estimated that 660,000 cases of cancer in the year 2008 were attributable to the bacterium Helicobacter pylori (H. pylori), corresponding to 5.2% of the 12.7 million total cancer cases that occurred worldwide. In recent years, evidence has accumulated that immunoblot (western blot) is more sensitive for detection of anti-H. pylori antibodies than ELISA, the detection method used in our previous analysis. The purpose of this short report is to update the attributable fraction (AF) estimate for H. pylori after briefly reviewing new evidence, and to reassess the global burden of cancer attributable to H. pylori. We therefore reviewed the literature for studies comparing the risk of developing non-cardia gastric cancer (NCGC) in cases and controls, using both ELISA and multiple antigen immunoblot for detection of H. pylori. The results from prospective studies were combined, and the new pooled estimates were applied to the calculation of the AF for H. pylori in NCGC, then to the burden of infection-related cancers worldwide. Using the immunoblot-based data, the worldwide AF for H. pylori in NCGC increased from 74.7% to 89.0%. This implies approximately 120,000 additional cases of NCGC attributable to H. pylori infection for a total of around 780,000 cases (6.2% instead of 5.2% of all cancers). These updated estimates reinforce the role of H. pylori as a major cause of cancer.

Prevalence of Helicobacter pylori infection worldwide: a systematic review of studies with national coverage

The systematic assessment of large population-based surveys addressing the prevalence of Helicobacter pylori infection may provide robust evidence for understanding the trends in the exposure to this major risk factor across settings with distinct patterns of gastric cancer variation. Our aim was to describe the prevalence of H. pylori infection in different countries and periods, through systematic review of the literature. We searched PubMed from inception up to September 2013 to identify original studies reporting on the prevalence of H. pylori, and only those evaluating samples with national coverage were included. We identified 37 eligible studies including data for 22 countries. The prevalences were higher in Central/South America and Asia, and at least two-fold higher in countries with high gastric cancer incidence. In most countries presenting data for different time periods, the prevalences were usually lower in the most recent surveys. However, there was little variation in settings where prevalences were already low. Among countries with high prevalence of H. pylori infection there is an ample scope for reducing its burden in the next decades, whereas further declines in settings with already low prevalences will require more intensive efforts.

Effect of Helicobacter pylori infection on growth of normal human liver cells (L-02)

AIM: To investigate the effect of Helicobacter pylori (H. pylori) infection on the growth of human normal liver cell line-02 (L-02) and the possible mechanisms involved.

METHODS: L-02 cells and H. pylori strains were cultured in vitro. CagA⁺ and CagA^-H. pylori strains were identified by PCR. After L-02 cells were incubated with different densities of CagA⁺ and CagA^-H. pylori strains for 24 h, MTT assay was used to detect the inhibition rate of L-02 cells, and the expression of transforming growth factor-beta typeⅠ(TβRⅠ) in L-02 cells was detected by real-time PCR. Cells without H. pylori infection were used as a negative control group.

RESULTS: Both CagA⁺ and CagA^-H. pylori strains significantly inhibited L-02 cell growth in a dose-dependent manner compared with the control group (P < 0.05). At the same concentration, CagA⁺H. pylori strain had a more significant inhibitory effect on L-02 cell growth than CagA⁺H. pylori strain (10¹ CFU/mL: 10.96 ± 0.231 vs 4.47 ± 0.289; 10² CFU/mL: 25.31 ± 0.398 vs 5.51 ± 0.168; 10³ CFU/mL: 33.13 ± 0.312 vs 10.33 ± 0.213; 10⁴ CFU/mL: 54.57 ± 0.245 vs 17.12 ± 0.309; 10⁵ CFU/mL: 79.45 ± 0.402 vs 25.83 ± 0.337; 10⁶ CFU/mL: 90.21 ± 0.271 vs 32.35 ± 0.178; P< 0.05 for all). Both CagA⁺ and CagA^-H. pylori strains significantly increased the expression of TβRⅠin a dose-dependent manner compared with the control group. At the same concentration, CagA⁺H. pylori strain increased the expression of TβRⅠmore significantly than CagA^-H. pylori strain (10¹ CFU/mL: 1.65 ± 0.101 vs 1.11 ± 0.110; 10² CFU/mL: 2.77 ± 0.198 vs 1.20 ± 0.203; 10³ CFU/mL: 4.59 ± 0.112 vs 1.59 ± 0.134; 10⁴ CFU/mL: 5.47 ± 0.145 vs 1.99 ± 0.331; 10⁵ CFU/mL: 7.45 ± 0.102 vs 2.65 ± 0.268; 10⁶ CFU/mL: 8.57 ± 0.221 vs 4.57 ± 0.161; P< 0.05 for all).

CONCLUSION: H. pylori infection inhibits the growth of L-02 cells in a dose-dependent manner, and the inhibitory effect of CagA⁺H. pylori strain was stronger than that of CagA^-H. pylori strain. H. pylori infection increases the expression of TβRⅠin L-02 cells in a dose-dependent manner, and CagA⁺H. pylori strain increases the expression of TβRⅠmore significantly. These findings suggest that H. pylori strain inhibits L-02 cell proliferation possibly by altering the expression of TβRⅠand disturbing the TGF-β1/Smad signal transduction pathway.

Sociodemographic determinants of prevalence and incidence of Helicobacter pylori infection in Portuguese adults

BACKGROUND

Understanding the determinants of Helicobacter pylori infection in adults is essential to predict the burden of H. pylori-related diseases. We aimed to estimate the prevalence and incidence of H. pylori infection and to identify its major sociodemographic correlates in an urban population from the North of Portugal.

MATERIAL AND METHODS

A representative sample of noninstitutionalized adult inhabitants of Porto (n = 2067) was evaluated by ELISA (IgG) and a subsample (n = 412) was tested by Western Blot to assess infection with CagA-positive strains. Modified Poisson and Poisson regression models were used to estimate crude and sex-, age-, and education-adjusted prevalence ratios (PR) and incidence rate ratios (RR), respectively.

RESULTS

The prevalence of H. pylori infection was 84.2% [95% confidence interval (95%CI): 82.4-86.1]. It increased across age-groups in the more educated subjects, (18-30 years: 72.6%; ≥71 years: 88.1%; p for trend <0.001) and decreased with education in the younger (≤4 schooling years: 100.0%; ≥10 schooling years: 72.6%; p for trend <0.001). Living in a more deprived neighborhood was associated with a higher prevalence of infection, only in the younger (PR = 1.20, 95%CI: 1.03-1.38) and more educated participants (PR = 1.15, 95%CI: 1.03-1.29). Among the infected, the proportion with CagA-positive strains was 61.7% (95%CI: 56.6-66.9). The incidence rate was 3.6/100 person-years (median follow-up: 3 years; 95%CI: 2.1-6.2), lower among the more educated (≥10 vs ≤9: RR = 0.25, 95%CI: 0.06-0.96). The seroreversion rate was 1.0/100 person-years (95%CI: 0.6-1.7).

CONCLUSIONS

The prevalence of infection among adults is still very high in Portugal, suggesting that stomach cancer rates will remain high over the next few decades.

Gastric adenocarcinoma in Zambia: a case-control study of HIV, lifestyle risk factors, and biomarkers of pathogenesis

BACKGROUND

Gastric cancer is a leading cause of cancer deaths worldwide but there are few data from Africa. We recently observed a trend towards diagnosis in younger patients.

OBJECTIVE

To test the hypothesis that HIV might have altered risk factors for acquisition of gastric cancer, in a case-control study in the University Teaching Hospital, Lusaka, Zambia.

METHODS

Patients (n=52) with confirmed gastric adenocarcinoma and controls (n=94) undergoing endoscopy but with no macroscopic gastric pathology. Established risk factors and HIV status were compared.

RESULTS

HIV status did not differ significantly between cases and controls (odds ratio 1.03; 95% CI 0.2 - 4.3; p=1.00) and seroprevalence in cases was similar to that of the Zambian population. Smoking, regular alcohol intake, and gastric atrophy were all associated with cancer in univariate and multivariate analysis. Helicobacter pylori serology was positive in 84% of patients studied and cagA serology in 66%; neither serological marker was associated with cancer. Atrophy was common in cases (57%) and controls (30%) and associated with both smoking and alcohol use. Intestinal metaplasia was present in 17% of the controls, but was not associated with atrophy.

CONCLUSIONS

HIV was not associated with gastric cancer and does not explain the apparent younger age distribution. Atrophy was common and was not essential for the development of intestinal metaplasia, suggesting that gastric carcinogenesis in Africa does not always follow the pathway from atrophy to intestinal metaplasia to gastric carcinoma (the so-called Correa pathway).

Helicobacter pylori virulence factors that act at different stages of infection

Helicobacter pylori (H. pylori) plays an essential role in the development of various gastroduodenal diseases, such as chronic superficial gastritis, peptic ulcer, gastric mucosa associated lymphoid tissue (MALT) lymphoma, and gastric adenocarcinoma. The diverse clinical outcomes after H. pylori infection are partly attributable to various H. pylori virulence factors. These virulence factors can act at different stages of infection, including (1) establishing successful colonization; (2) evading the host's immune system and (3) invading the gastric mucosa. In this paper, we review the recent advances in research of H. pylori virulence factors associated with the pathogenic process of H. pylori infection.

Prediagnosis lifestyle exposures and survival of gastric cancer patients: a cohort study from Portugal

BACKGROUND

Dietary habits and smoking are recognised as important gastric cancer determinants. However, their impact on prognosis remains poorly understood. We aimed to quantify the association between lifestyles and survival of gastric cancer patients.

METHODS

In 2001-2006, 568 patients were recruited in the two major public hospitals in the north of Portugal. Participants were inquired about smoking and dietary habits regarding the year preceding the diagnosis. The vital status of all participants, up to 2011 (maximum follow-up: 10 years), was assessed through the North Region Cancer Registry. Cox proportional hazards regression models were used to estimate adjusted (at least for age, sex and education) hazard ratios (HR) and 95% confidence intervals (95% CI).

RESULTS

No significant differences in gastric cancer survival were observed according to smoking status (current vs never smokers, HR=1.00, 95% CI: 0.72-1.38) or alcohol intake (current vs never consumers, HR=0.87, 95% CI: 0.61-1.25). Only a dietary pattern (high consumptions of most food groups and low vegetable soup intake) was significantly associated with a better prognosis among patients with the extent of disease classified as regional spread (HR=0.45, 95% CI: 0.22-0.93).

CONCLUSION

This study shows that prediagnosis lifestyles have a small impact in the survival of gastric cancer patients.

Effect of annual endoscopic screening on clinicopathologic characteristics and treatment modality of gastric cancer in a high-incidence region of Korea

We investigated risk factors for gastric cancer (GC) and effect of annual endoscopic screening on detection and treatment modality of GC. Asymptomatic adults who underwent upper endoscopy during health checkups at Seoul National University Hospital Healthcare System Gangnam Center were enrolled. We compared clinicopathologic characteristics of GC according to screening interval (repeated vs. infrequent, annual vs. biennial). After age- and sex-matching, relative risk was computed by hazard ratio (HR) using Cox proportional regression with multivariate adjustment. Of the 58,849 subjects who received screening endoscopy, 277 (0.47%) were found to have GC. Intestinal type comprised 55.4% (102/184) followed by diffuse type (n = 65, 35.3%). Age ≥ 50 years, family history and smoking independently increased the risk of GC for both types, whereas male gender [HR = 4.81, 95% confidence interval (CI): 2.72-8.03] and intestinal metaplasia (IM) (HR = 10.87, 95% CI: 3.36-22.30) were significant predictors for intestinal type only. Proportion of early gastric cancer (EGC) was 98.6% (71/72) in annual screening group and 80.7% (46/57) in biennial screening group (p < 0.01). In the former, tumor size was smaller (1.7 ± 1.3 vs. 2.3 ± 1.8 cm; p < 0.01] and proportion of intramucosal cancer was larger (75.0 vs. 56.1%; p = 0.04). Endoscopic resection was performed more frequently in annual screening group (56.9 vs. 33.3%; p = 0.02). IM along with male gender and older age was a strong risk factor for intestinal type GC. Annual screening group improved detection of early-stage and endoscopically treatable GC suggesting that intensive screening and surveillance may be useful for high-risk subpopulations with epidemiologic risk factors or premalignant lesions such as IM.

Differential distribution of the PPIase gene in Helicobacter pylori strains isolated from patients with different gastric diseases

AIM: To explore the distribution of the peptidyl-prolyl cis-trans isomerase (PPIase) gene in Helicobacter pylori (H. pylori) strains isolated from patients with different gastric diseases.

METHODS: Biopsy specimens were taken from the gastric mucosa of patients with superficial gastritis (GS), atrophic gastritis (GA) or gastric cancer (GC) and used to isolate a total of 64 H. pylori strains. The distribution of the PPIase gene in these strains was analyzed by PCR.

RESULTS: The GA group had the highest distribution frequency (94.4%) of the PPIase gene, which was significantly higher than those in the GS (57.7%) and GC (65.0%) groups (P = 0.014, 0.045). Although the frequency of the PPIase gene was higher in the GC group than in the GS group, there was no statistical difference between them (P > 0.05).

CONCLUSION: H. pylori strains isolated from patients with AG carried a higher frequency of the PPIase gene.

Diagnosis of Helicobacter pylori Infection

When an endoscopy is performed, it now becomes easier to observe indirect evidence of the presence of a Helicobacter pylori infection, given the progress of new methods including magnifying narrow band imaging or confocal laser endomicroscopy. Out of the biopsy-based tests, the novel original method proposed concerned culture in a broth medium with or without antibiotics and ELISA detection of H. pylori. New stool antigen tests are still appearing with no major improvement in comparison with the monoclonal-based tests already on the market. The combination of pepsinogen detection to H. pylori serology is now more and more evaluated to detect preneoplastic lesions.

Salt intake and gastric cancer risk according to Helicobacter pylori infection, smoking, tumour site and histological type

BACKGROUND

Although salt intake is considered a probable risk factor for gastric cancer, relevant studies have provided heterogeneous results, and the magnitude of the association has not been accurately quantified.

METHODS

To quantify gastric cancer risk in relation to dietary salt exposure according to Helicobacter pylori infection status and virulence, smoking, tumour site, and histological type, we evaluated 422 gastric cancer cases and 649 community controls. Salt exposure was estimated in the year before the onset of symptoms through: sodium intake (estimated by a food frequency questionnaire (FFQ)); main food items/groups contributing to dietary sodium intake; visual analogical scale for salt intake preference; use of table salt; and duration of refrigerator ownership.

RESULTS

Comparing subjects with the highest with those with the lowest salt exposure (3rd vs 1st third), sodium intake (OR=2.01, 95% CI: 1.16-3.46), consumption of food items with high contribution to sodium intake (OR=2.54, 95% CI: 1.56-4.14) and salt intake evaluated by visual analogical scale (OR=1.83, 95% CI: 1.28-2.63) were associated with an increased gastric cancer risk. Subjects owning a refrigerator for >50 years had a lower risk for gastric cancer (OR=0.28, 95% CI: 0.14-0.57). These associations were observed regardless of H. pylori infection status and virulence, smoking, tumour site or histological type.

CONCLUSION

Our results support the view that salt intake is an important dietary risk factor for gastric cancer, and confirms the evidence of no differences in risk according to H. pylori infection and virulence, smoking, tumour site and histological type.

Helicobacter pylori infection and gastric cardia cancer: systematic review and meta-analysis

OBJECTIVE

Helicobacter pylori infection is the most important risk factor for gastric cancer, but no association with cardia cancer has been recognized. However, a heterogeneous distribution of etiologically distinct types of cardia cancer may contribute to explain conflicting findings between studies in high- and low-risk settings. We aimed to quantify the association between H. pylori infection and gastric cardia cancer through meta-analysis, and to provide an explanation for the expected heterogeneity of results.

METHODS

We systematically reviewed published studies addressing the association between H. pylori infection and gastric cardia cancer (up to June 2009), and extracted relative risk (RR) estimates for the association with cardia and non-cardia cancers. Summary RR estimates and 95% confidence intervals (95% CI) were computed using random-effects models. Subgroup analyses were conducted, namely according to gastric cancer risk settings.

RESULTS

Thirty-four articles were considered for meta-analysis. For cardia cancer, summary RR was 1.08 (95% CI 0.83-1.40; I (2) = 52.8%), higher in high-risk (RR = 1.98; 95% CI 1.38-2.83; I (2) = 18.4%) than in low-risk settings (RR = 0.78; 95% CI 0.63-0.97; I (2) = 11.6%). For non-cardia cancer, RR estimates were similar in high- (RR = 3.02; 95% CI 1.92-4.74; I (2) = 90.7%) and low-risk settings (RR = 2.56; 95% CI 1.99-3.29; I (2) = 46.6%). These observations were consistent across different inclusion criteria and when accounting for the virulence of the infecting strains.

CONCLUSIONS

In high-risk settings, a positive association between H. pylori infection and gastric cancer was observed both for cardia and non-cardia cancers. The results support the hypothesis of a heterogeneous distribution of etiologically distinct types of cardia cancer.