Smoking, Helicobacter pylori virulence, and type of intestinal metaplasia in Portuguese males

Risk factors in the development of gastric adenocarcinoma in the general population: A cross-sectional study of the Wuwei Cohort

Several risk factors have been identified for the development of gastric adenocarcinoma (GAC), where the control group was usually a healthy population. However, it is unclear at what stage known risk factor exert their influence toward the progression to cancer. Based on the Wuwei Cohort, we enrolled 1,739 patients with chronic non-atrophic gastritis (no-CAG), 3,409 patients with chronic atrophic gastritis (CAG), 1,757 patients with intestinal metaplasia (IM), 2,239 patients with low-grade dysplasia (LGD), and 182 patients with high-grade dysplasia (HGD) or GAC to assess the risk factors between each two consecutive stages from no-CAG to GAC/HGD using adjusted logistic regression. We found that different groups of risk factors were associated with different stages. Age, occupation of farmer, low annual family income, Helicobacter pylori (H. pylori) infection, drinking, eating hot food, histories of gastritis and peptic ulcer were associated with the development of CAG. Age, illiteracy, H. pylori infection, smoking, eating hot food, eating quickly, and histories of gastritis and gallbladder diseases were associated with the progression to IM from CAG. Male, occupation of farmer and history of peptic ulcer were associated with the development of LGD from IM. Age, male and polyp history appeared to be risk factors associated with the development of GAC/HGD from LGD. In conclusion, it seems that most risk factors function more as a set of switches that initiated the GAC carcinogenesis. H. Pylori eradication and control of other risk factors should be conducted before IM to decrease the incidence of GAC.

Chinese integrated guideline on the management of gastric precancerous conditions and lesions

The standardized diagnosis and management of gastric precancerous conditions and lesions are important to prevent gastric cancer. This guideline, created by 5 traditional Chinese medicine and Western medicine associations, based on the current morbidity and diagnosis and treatment of gastric precancerous conditions and lesions, provides specific key points and strategies for diagnosis and treatment in the following five aspects: definition and epidemiology, diagnosis and stage, surveillance, treatment and efficacy evaluation. It is hoped that these aspects, assessed by integrating Western medicine and traditional Chinese medicine and involving multidisciplinary participation, will play a guiding role in clinical diagnosis and treatment and achieve effective secondary prevention of gastric cancer.

Associations of lung cancer risk with biomarkers of Helicobacter pylori infection

Helicobacter pylori infection has been suggested to be associated with lung cancer risk. However, information is lacking on whether the association differs by H. pylori antigen. We conducted a nested case-control study within the Southern Community Cohort Study, including 295 incident lung cancer cases and 295 controls. Helicobacter pylori multiplex serology assay was performed to detect antibodies to 15 H. pylori proteins. Conditional logistic regression was used to estimate odds ratios (ORs) and confidence intervals (95% CIs) after adjustment for covariates. Overall H. pylori+ was associated with a non-statistically significant increased risk of lung cancer (OR: 1.29; 95% CI: 0.85-1.95). Significant associations, however, were observed for H. pylori+ VacA+ (OR: 1.64; 95% CI: 1.02-2.62) and H. pylori+ Catalase+ (OR: 1.75; 95% CI: 1.11-2.77). The positive association of H. pylori+ Catalase+ with lung cancer risk was predominantly seen among African Americans (OR: 2.09; 95% CI: 1.11-3.95) but not European Americans (OR: 1.20; 95% CI: 0.56-2.54). Among participants who smoked ≥ 30 pack-years, overall H. pylori+ (OR: 1.85; 95% CI: 1.02-3.35), H. pylori+ CagA+ (OR: 2.77; 95% CI: 1.35-5.70), H. pylori+ VacA+ (OR: 2.53; 95% CI: 1.25-5.13) and H. pylori+ HP1564+ (OR: 2.01; 95% CI: 1.07-3.77) were associated with increased risk of lung cancer. Our study provides novel evidence that associations of H. pylori infection with lung cancer risk differ by H. pylori biomarker, may be more evident among African Americans and may be modified by smoking habits. Furthermore, studies are warranted to confirm our findings.

Mechanisms of the Epithelial-Mesenchymal Transition and Tumor Microenvironment in Helicobacter pylori-Induced Gastric Cancer

Helicobacter pylori (H. pylori) is one of the most common human pathogens, affecting half of the world’s population. Approximately 20% of the infected patients develop gastric ulcers or neoplastic changes in the gastric stroma. An infection also leads to the progression of epithelial–mesenchymal transition within gastric tissue, increasing the probability of gastric cancer development. This paper aims to review the role of H. pylori and its virulence factors in epithelial–mesenchymal transition associated with malignant transformation within the gastric stroma. The reviewed factors included: CagA (cytotoxin-associated gene A) along with induction of cancer stem-cell properties and interaction with YAP (Yes-associated protein pathway), tumor necrosis factor α-inducing protein, Lpp20 lipoprotein, Afadin protein, penicillin-binding protein 1A, microRNA-29a-3p, programmed cell death protein 4, lysosomal-associated protein transmembrane 4β, cancer-associated fibroblasts, heparin-binding epidermal growth factor (HB-EGF), matrix metalloproteinase-7 (MMP-7), and cancer stem cells (CSCs). The review summarizes the most recent findings, providing insight into potential molecular targets and new treatment strategies for gastric cancer.

Risk factors for gastric precancerous and cancers lesions in Latin American counties with difference gastric cancer risk

OBJECTIVE

To evaluate the risk factors associated with pre-neoplastic lesions and gastric cancer in countries with different cancer risk in Latin America.

METHODS

1222 questionnaires of risk factors related to pre-neoplastic lesions and gastric cancer were obtained from patients from Mexico (N = 559), Colombia (N = 461) and Paraguay (N = 202), who were treated at the gastroenterology or oncology service of participant hospitals. In addition, biopsies specimens to establish histological diagnosis and blood to detect IgG antibodies against Helicobacter-pylori (H. pylori) whole-cell antigens and CagA protein using an ELISA were collected. These consisted of 205 gastric cancer, 379 pre-neoplastic (intestinal metaplasia (IM) / atrophic gastritis) and 638 control (normal /non-atrophic gastritis) cases. The odds ratio (OR) and 95% confidence intervals (CI) associated with potential risk factors were estimated by polynomial logistic regression model.

RESULTS

Seropositivity to H. pylori was associated with risk of pre-neoplastic lesions, with OR = 1.9 (CI 95% 1.2-2.9; p = 0.006). Grain / cereal intake (OR = 1.6, 95% CI 1.0-2.5 ; p = 0.049) and egg intake (OR = 1.7 95% CI 1.1-2.6 ; p = 0.021) were related to gastric cancer. Among, people who did not developed gastric cancer, smoking more than five cigarette per day had the highest risk of being infected by H. pylori (OR = 1.9; CI 95% 1.1-3.3 ; p = 0.028).

CONCLUSION

The present study in Latin American countries confirmed that similar environmental factors such as smoking and grain/cereal consumption were associated with H. pylori infection and its induced gastric lesions as reported in other regions where dominant H. pylori strains differ.

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.

Smoking and Urinary Cotinine Levels Are Predictors of Increased Risk for Gastric Intestinal Metaplasia

Studies on a longitudinal relationship between smoking status and intestinal metaplasia (IM), a premalignant lesion of stomach cancer, are limited. Here we examined the association of smoking status and urinary cotinine levels, an objective measure of smoking, with the development of endoscopic IM. This cohort study included 199,235 Korean adults free of endoscopic IM who underwent upper endoscopy at baseline and subsequent visits and who were followed for up to 6.8 years (median, 3.7 years). Former and current smoking status and pack-years based on self-reports were associated with an increased risk of new-onset IM in men but not in women. However, urinary cotinine levels were positively associated with incident IM in a dose-response manner in both men and women. For men, the multivariable-adjusted HR [95% confidence interval (CI)] for incident IM comparing the urinary cotinine levels of 50 to 99 ng/mL, 100 to 499 ng/mL, and ≥500 ng/mL with <50 ng/mL were 1.20 (0.94-1.55), 1.26 (1.14-1.40), and 1.54 (1.44-1.64), respectively, whereas for women, corresponding HR (95% CI) were 0.75 (0.19-2.99), 1.86 (1.20-2.88), and 1.57 (1.07-2.30), respectively. These associations were observed when changes in smoking status and other confounders were updated during follow-up as time-varying covariates. In this large cohort of young and middle-aged men and women, urinary cotinine levels were independently associated with an increased incidence of endoscopic IM in a dose-response manner. Collectively, these data confirm smoking as an independent risk factor for the development of gastric IM, a precursor lesion of stomach cancer. SIGNIFICANCE: A large-scale cohort study of nearly 200,000 adults associates smoking with increased risk for gastric intestinal metaplasia, a precursor lesion of stomach cancer.

Factors Associated With Metachronous Gastric Cancer Development After Endoscopic Submucosal Dissection for Early Gastric Cancer

GOALS

To clarify the factors associated with metachronous gastric cancer development after endoscopic submucosal dissection (ESD) for early gastric cancer.

BACKGROUND

Patients who undergo ESD for early gastric cancer have an appreciable risk of developing metachronous gastric cancer. However, there have been few reports on the association between life style and the development of such cancer.

STUDY

Patients with early gastric cancer who underwent ESD at our institution between 2003 and 2012 were enrolled. Metachronous gastric cancer was defined as secondary gastric cancer detected >1 year after initial ESD. Factors, including age, gender, body mass index, eradication of Helicobacter pylori, cigarette smoking, drinking, and continuous use of a proton pump inhibitor, associated with metachronous gastric cancer development were evaluated by Cox proportional hazard regression analysis.

RESULTS

A total of 539 patients with a mean 53.6-month follow-up period were analyzed. The 5-year cumulative incidence of secondary gastric cancer was 13.0%. Multivariate analysis exhibited that age of 60 years and above [hazard ratio (95% confidence interval)=4.05 (1.23-13.4)] and cigarette smoking [2.12 (1.19-3.78)] were independent risk factors for metachronous gastric cancer development. Furthermore, ≥20 pack-years of smoking [1.51 (1.03-2.24)] was a significant risk factor with a dose-response relationship (P for trend=0.042). There was no significant association between Helicobacter pylori eradication and metachronous gastric cancer development.

CONCLUSIONS

This is the first study to demonstrate the detailed association between cigarette smoking and metachronous gastric cancer development.

The Gastric Microbiome and Its Influence on Gastric Carcinogenesis: Current Knowledge and Ongoing Research

Gastric malignancies are a leading cause of cancer-related death worldwide. At least 2 microbial species are currently linked to carcinogenesis and the development of cancer within the human stomach. These include the bacterium Helicobacter pylori and the Epstein-Barr virus. In recent years, there has been increasing evidence that within the human gastrointestinal tract it is not only pathogenic microbes that impact human health but also the corresponding autochthonous microbial communities. This article reviews the gastrointestinal microbiome as it relates primarily to mechanisms of disease and carcinogenesis within the upper gastrointestinal tract.

Risk factors for intestinal metaplasia in a southeastern Chinese population: an analysis of 28,745 cases

PURPOSE

To identify risk factors for intestinal metaplasia in a southeastern Chinese population.

METHODS

Subjects who underwent upper GI endoscopy and endoscopic biopsy in the First Affiliated Hospital of Nanjing Medical University from 2008 to 2013 were included into this study. Various demographic, geographic, clinical and pathological data were analyzed separately to identify risk factors for intestinal metaplasia.

RESULTS

The incidence of intestinal metaplasia differed significantly in 17 municipal areas ranging from 16.79 to 38.56% and was positively correlated with the age range of 40-70 years, male gender, gastric ulcer, bile reflux, Helicobacter pylori infection, atrophic gastritis, dysplasia, gastric cancer, degree of chronic and acute inflammation, and gross domestic product per capita (P < 0.01). Multivariate linear regression analysis indicated that only gross domestic product per capita revealed a significant difference in the incidence of intestinal metaplasia among all factors mentioned.

CONCLUSION

This study confirms age, male gender, gastric ulcer, bile reflux, H. pylori infection, severe degree of chronic and acute inflammation to be the risk factors for intestinal metaplasia. We speculate that the gross domestic product per capita of different areas may be a potential independent risk factor impacting the incidence of intestinal metaplasia.

Helicobacter pylori vacuolating cytotoxin genotypes and preneoplastic lesions or gastric cancer risk: a meta-analysis

BACKGROUND AND AIM

Disease progression to gastric cancer (GC) occurs in only a small proportion of Helicobacter pylori (H.  pylori) infected patients. The bacterium vacuolating cytotoxin A (vacA) gene polymorphisms may determine the clinical consequences. We examined the strength of this association in adult-infected populations and modeled the impact of mean age-standardized incidence rates (ASRs) of GC as a hypothesized moderator variable.

METHODS

Pooled relative risk (RR) estimates were calculated. Subgroup, sensitivity, and meta-regression analyses were conducted.

RESULTS

Totally, 33 studies (1446 cases/2697 controls) were analyzed. The vacA-s1 genotype was significantly associated with an increased risk of atrophic gastritis(AG), intestinal metaplasia(IM), and GC (RR = 1.116, 95% CI, 1.019-1.222; RR = 1.418, 95% CI, 1.035-1.942; and RR = 1.333, 95% CI, 1.115-1.593, respectively); however, the vacA m1 genotype strongly increased the risk of IM and GC, but not AG (RR = 1.571, 95% CI, 1.247-1.980 and RR = 1.431, 95% CI, 1.180-1.735, respectively). The vacA s1m1 allelic combination was linked to an increased risk of GC. The m1-type of vacA was more potent than s1 for predicting the risk of GC within the subgroups with the mean ASRs of 11/100,000-19/100,000 and less than 10/100,000. The meta-regression analysis indicated that the ASR of GC modified the association between H.  pylori genotypes and GC risk, where the estimated risk was significantly decreased with increasing the mean ASRs of GC (P-values = 0.025, 0.00009, and 0.0005 for s1, m1, and s1m1, respectively).

CONCLUSIONS

The H. pylori vacA-s1 and vacA-m1 allelic variants strongly increased susceptibility to IM and GC; however, only s1 showed an association with AG. These associations were largely influenced by geographic variations in the GC incidence rate.

Relationship between tobacco, cagA and vacA i1 virulence factors and bacterial load in patients infected by Helicobacter pylori

Background and Aim

Several biological and epidemiological studies support a relationship between smoking and Helicobacter pylori (H. pylori) to increase the risk of pathology. However, there have been few studies on the potential synergistic association between specific cagA and vacA virulence factors and smoking in patients infected by Helicobacter pylori. We studied the relationship between smoking and cagA, vacA i1 virulence factors and bacterial load in H. pylori infected patients.

Methods

Biopsies of the gastric corpus and antrum from 155 consecutive patients in whom there was clinical suspicion of infection by H. pylori were processed. In 106 patients H. pylori infection was detected. Molecular methods were used to quantify the number of microorganisms and presence of cagA and vacA i1 genes. A standardized questionnaire was used to obtain patients’ clinical data and lifestyle variables, including tobacco and alcohol consumption. Adjusted Odds Ratios (OR_adjusted) were estimated by unconditional logistic regression.

Results

cagA was significantly associated with active-smoking at endoscope: OR_adjusted 4.52. Evidence of association was found for vacA i1 (OR_adjusted 3.15). Bacterial load was higher in active-smokers, although these differences did not yield statistical significance (median of 262.2 versus 79.4 copies of H. pylori per cell).

Conclusions

The association between smoking and a higher risk of being infected by a virulent bacterial population and with higher bacterial load, support a complex interaction between H. pylori infection and environmental factors.

Association of smoking, alcohol and NSAIDs use with expression of cag A and cag T genes of Helicobacter pylori in salivary samples of asymptomatic subjects

OBJECTIVE

To determine the association of smoking, alcohol and nonsteroidal anti-inflammatory drugs (NSAIDs) use with presence and virulence of Helicobacter pylori (H. pylori) infection in a representative sample of a random adult population of asymptomatic subjects.

METHODS

Non virulent 16S rRNA and virulent cag A and T genes from salivary samples of 854 asymptomatic subjects were determined using polymerase chain reaction. The presence and absence of virulent and non virulent infection was statistically compared with consumption of smoking, alcohol and NSAIDs.

RESULTS

The prevalence of infection in male and female subjects was found to be 69.25% and 66.90%, respectively. The prevalence of infection in the population of asymptomatic subjects with respect to consumption of alcohol was as follows: current (31.22%), former (52.20%) and never (43.58%). The prevalence of infection in the population of asymptomatic subjects with respect to smoking of cigarettes was as follows: current (88.80%), former (57.14%) and never (33.33%). The prevalence of infection in the subject population consuming NSAIDs and not consuming NSAIDs frequently was found to be 82.75% and 21.16%, respectively. Virulence in male and female subjects was found to be 60.00% and 50.00%, respectively. The presence of virulent infection in the population of asymptomatic subjects with respect to consumption of alcohol was as follows: current (28.57%), former (40.15%) and never (50.00%). The prevalence of virulent infection in the population of asymptomatic subjects with respect to smoking of cigarettes was as follows: current (79.32%), former (75.00%) and never (50.00%). The prevalence of virulent infection in the subject population consuming NSAIDs and not consuming NSAIDs frequently was found to be 88.23% and 66.66%, respectively.

CONCLUSIONS

It can be concluded that smoking and NSAIDs consumption are aggravating factors for virulence of H. pylori and alcohol can inhibit H. pylori infection in asymptomatic subjects.

Tobacco smoking and intestinal metaplasia: Systematic review and meta-analysis

BACKGROUND

The evaluation of specific risk factors for early endpoints in the gastric carcinogenesis pathway may further contribute to the understanding of gastric cancer aetiology.

AIMS

To quantify the relation between smoking and intestinal metaplasia through systematic review and meta-analysis.

METHODS

Articles providing data on the association between smoking and intestinal metaplasia were identified in PubMed(®), Scopus(®) and Web of Science™, searched until April 2014, and through backward citation tracking. Summary odds ratio estimates and 95% confidence intervals were computed using the DerSimonian and Laird method. Heterogeneity was quantitatively assessed using the I(2) statistic.

RESULTS

A total of 32 articles were included in this systematic review and 19 provided data for meta-analysis. Smoking was defined as ever vs. never (crude estimates, six studies, summary odds ratio=1.54, 95% confidence interval: 1.12-2.12, I(2)=67.4%; adjusted estimates, seven studies, summary odds ratio=1.26, 95% confidence interval: 0.98-1.61, I(2)=65.0%) and current vs. non-smokers (crude estimates, seven studies, summary odds ratio=1.27, 95% confidence interval: 0.88-1.84, I(2)=73.4%; adjusted estimates, two studies, summary odds ratio 1.49, 95% confidence interval: 0.99-2.25, I(2)=0.0%).

CONCLUSION

The weak and non-statistically significant association found through meta-analysis of the available evidence does not confirm smoking as an independent risk factor for intestinal metaplasia.

Prevalence of gastric precancerous conditions: a systematic review and meta-analysis

Several reports of estimates for precancerous conditions for gastric adenocarcinoma can be found in the current literature. Our aim was to systematically review and estimate the prevalence of gastric precancerous conditions. Four databases (PubMed, Scopus, Web of Knowledge and EBSCO Academic Search Complete) were searched for original manuscripts addressing the presence of chronic atrophic gastritis (CAG) or intestinal metaplasia (IM). Subgroup analysis was carried out on methods of diagnosis, type of population, incidence of gastric cancer, sex, Helicobacter pylori status, age and extent of conditions. Overall, 107 studies were included. The worldwide prevalence of CAG in the general population was 33% (95% confidence interval: 26-41%) when considering biopsies (n=20 912) and 24% (19-29%) if serology (n=51 886) was used, whereas IM was found in 25% (19-30%) (n=30 960). Estimates for CAG were higher in countries with a high incidence of gastric cancer (42 vs. 23%), men (32 vs. 28%), H. pylori positive (46 vs. 17%) and if aged 40 years or older (48 vs. 22%). The prevalence of extensive conditions was 16% (12-20%) for CAG and 13% (9.0-17%) for IM. When comparing countries with high versus low to moderate incidence of gastric cancer, significant differences were achieved for CAG: 27% (12-36%) versus 7.3% (5.6-9.0%). Worldwide, one-third and one-fourth of individuals may harbour CAG and IM, respectively. In countries with a high incidence of gastric cancer, the prevalence of extensive conditions may increase up to 27% and these patients represent a high-risk population to whom endoscopic surveillance should be offered according to recent guidelines.

Increase in genogroup II.4 norovirus host spectrum by CagA-positive Helicobacter pylori infection

BACKGROUND

Noroviruses (NoVs) represent a considerable public health burden. Despite their enormous genetic diversity, most outbreaks are due to the single GII.4 genotype, but the reasons for this are poorly understood. NoVs use histo-blood group antigens (HBGAs) as attachment factors. Since HBGAs are present in saliva, binding of strains to saliva is commonly used as a surrogate for recognition of the gut surface by specific strains, although the relationship between saliva and gut tissue expression of HBGAs is not well defined.

METHODS

The presence of fucosylated HBGAs in saliva and stomach biopsy specimens, as well as that of genogroup I.1 and genogroup II.4 virus-like particles, were compared in a series of 109 donors from Portugal.

RESULTS

An overall good concordance between HBGA expression in saliva and stomach surface mucosa was observed. However, unexpected mucosal expression of α(1,2)fucosylated epitopes in nonsecretor individuals was frequently detected, allowing for GII.4 attachment. Although all individuals were infected with Helicobacter pylori, abnormal expression of α(1,2)fucosylated motifs and binding of GII.4 virus-like particles in nonsecretors' mucosa were associated with positivity for the H. pylori CagA virulence factor.

CONCLUSIONS

Infection by CagA-positive H. pylori induces expression of GII.4 attachment factors in nonsecretors' mucosa, expanding the host range of these strains and thereby possibly contributing to their epidemiological dominance.

Neglected role of hookah and opium in gastric carcinogenesis: a cohort study on risk factors and attributable fractions

A recent study showed an association between hookah/opium use and gastric cancer but no study has investigated the relationship with gastric precancerous lesions. We examined the association between hookah/opium and gastric precancerous lesions and subsequent gastric cancer. In a population-based cohort study, 928 randomly selected, healthy, Helicobacter pylori-infected subjects in Ardabil Province, Iran, were followed for 10 years. The association between baseline precancerous lesions and lifestyle risk factors (including hookah/opium) was analyzed using logistic regression and presented as odds ratios (ORs) and 95% confidence intervals (CIs). We also calculated hazard ratios (HRs) and 95% CIs for the associations of lifestyle risk factors and endoscopic and histological parameters with incident gastric cancers using Cox regression models. Additionally, the proportion of cancers attributable to modifiable risk factors was calculated. During 9,096 person-years of follow-up, 36 new cases of gastric cancer were observed (incidence rate: 3.96/1,000 persons-years). Opium consumption was strongly associated with baseline antral (OR: 3.2; 95% CI: 1.2-9.1) and body intestinal metaplasia (OR: 7.3; 95% CI: 2.5-21.5). Opium (HR: 3.2; 95% CI: 1.4-7.7), hookah (HR: 3.4; 95% CI: 1.7-7.1) and cigarette use (HR: 3.2; 95% CI: 1.4-7.5), as well as high salt intake, family history of gastric cancer, gastric ulcer and histological atrophic gastritis and intestinal metaplasia of body were associated with higher risk of gastric cancer. The fraction of cancers attributable jointly to high salt, low fruit intake, smoking (including hookah) and opium was 93% (95% CI: 83-98). Hookah and opium use are risk factors for gastric cancer as well as for precancerous lesions. Hookah, opium, cigarette and high salt intake are important modifiable risk factors in this high-incidence gastric cancer area.

Smoking and HIV-related health issues among older HIV-positive gay, bisexual, and other men who have sex with men

The prevalence of cigarette smoking and the relations between smoking and HIV clinical markers, HIV medication adherence, and opportunistic infections (OIs) were examined in a sample of 199 HIV-positive, gay, bisexual, and other men who have sex with men (MSM) aged 50 and older. Overall, 35.7% were current smokers, 35.7% were former smokers, and 28.6% were never smokers. In the final multivariable polytomous logistic regression model controlling for age, income, and illicit drug use, current smokers were less likely to report an undetectable viral load as compared to never and former smokers. Relative to never smokers, former smokers were more likely to report respiratory OIs, and current smokers were more likely to report gastrointestinal OIs. This study demonstrates high prevalence of cigarette smoking among aging, HIV-positive MSM and provides additional evidence for a relationship between smoking and poorer HIV clinical markers. Targeted and tailored smoking cessation programs within the context of HIV care services are warranted.

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.

Association between selected oral pathogens and gastric precancerous lesions

We examined whether colonization of selected oral pathogens is associated with gastric precancerous lesions in a cross-sectional study. A total of 119 participants were included, of which 37 were cases of chronic atrophic gastritis, intestinal metaplasia, or dysplasia. An oral examination was performed to measure periodontal indices. Plaque and saliva samples were tested with real-time quantitative PCR for DNA levels of pathogens related to periodontal disease (Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Actinobacillus actinomycetemcomitans) and dental caries (Streptococcus mutans and S. sobrinus). There were no consistent associations between DNA levels of selected bacterial species and gastric precancerous lesions, although an elevated but non-significant odds ratio (OR) for gastric precancerous lesions was observed in relation to increasing colonization of A. actinomycetemcomitans (OR = 1.36 for one standard deviation increase, 95% Confidence Interval = 0.87-2.12), P. gingivalis (OR = 1.12, 0.67-1.88) and T. denticola (OR = 1.34, 0.83-2.12) measured in plaque. To assess the influence of specific long-term infection, stratified analyses by levels of periodontal indices were conducted. A. actinomycetemcomitans was significantly associated with gastric precancerous lesions (OR = 2.51, 1.13-5.56) among those with ≥ median of percent tooth sites with PD ≥ 3 mm, compared with no association among those below the median (OR = 0.86, 0.43-1.72). A significantly stronger relationship was observed between the cumulative bacterial burden score of periodontal disease-related pathogens and gastric precancerous lesions among those with higher versus lower levels of periodontal disease indices (p-values for interactions: 0.03-0.06). Among individuals with periodontal disease, high levels of colonization of periodontal pathogens are associated with an increased risk of gastric precancerous lesions.

Estimating the prevalence of active Helicobacter pylori infection in a rural community with global positioning system technology-assisted sampling

We investigated a possible outbreak of H. pylori in a rural Northern Plains community. In a cross-sectional survey, we randomly sampled 244 households from a geocoded emergency medical system database. We used a complex survey design and global positioning system units to locate houses and randomly selected one eligible household member to administer a questionnaire and a 13C-urea breath test for active H. pylori infection (n = 166). In weighted analyses, active H. pylori infection was detected in 55·0% of the sample. Factors associated with infection on multivariate analysis included using a public drinking-water supply [odds ratio (OR) 12·2, 95% confidence interval (CI) 2·9-50·7] and current cigarette smoking (OR 4·1, 95% CI 1·7-9·6). People who lived in houses with more rooms, a possible indicator of decreased crowding in the home, were less likely to have active H. pylori infections (OR 0·7, 95% CI 0·5-0·9 for each additional room).

Association between oral health and gastric precancerous lesions

Although recent studies have suggested that tooth loss is positively related to the risk of gastric non-cardia cancer, the underlying oral health conditions potentially responsible for the association remain unknown. We investigated whether clinical and behavioral measures of oral health are associated with the risk of gastric precancerous lesions. We conducted a cross-sectional study of 131 patients undergoing upper gastrointestinal endoscopy. Cases were defined as those with gastric precancerous lesions including intestinal metaplasia or chronic atrophic gastritis on the basis of standard biopsy review. A validated structured questionnaire was administered to obtain information on oral health behaviors. A comprehensive clinical oral health examination was performed on a subset of 91 patients to evaluate for periodontal disease and dental caries experience. A total of 41 (31%) cases of gastric precancerous lesions were identified. Compared with non-cases, cases were significantly more likely to not floss their teeth [odds ratio (OR) = 2.89, 95% confidence interval (CI): 1.09-7.64], adjusting for age, sex, race, body mass index, smoking status, educational attainment and Helicobacter pylori status in serum. Among participants who completed the oral examination, cases (n = 28) were more likely to have a higher percentage of sites with gingival bleeding than non-cases [OR = 2.63, 95% CI: 1.37-5.05 for a standard deviation increase in bleeding sites (equivalent to 19.7%)], independent of potential confounders. Our findings demonstrate that specific oral health conditions and behaviors such as gingival bleeding and tooth flossing are associated with gastric precancerous lesions.

Stomach cancer screening and preventive behaviors in relatives of gastric cancer patients

AIM: To investigate gastric cancer screening and preventive behaviors among the relatives of patients with gastric cancer [i.e., gastric cancer relatives (GCRs)].

METHODS: We examined the Korean National Health and Nutrition Examination Survey 2005 (KNHANES III) database and compared the gastric cancer screening and preventive behaviors of GCRs (n = 261) with those of non-GCRs (n = 454) and controls without a family history of cancer (n = 2842).

RESULTS: The GCRs were more likely to undergo gastric cancer screening compared with the control group (39.2% vs 32.3%, adjusted odds ratio: 1.43, CI: 1.05-1.95), although the absolute screening rate was low. Dietary patterns and smoking rates did not differ significantly between the groups, and a high proportion of GCRs reported inappropriate dietary habits (i.e., approximately 95% consumed excessive sodium, 30% were deficient in vitamin C, and 85% were deficient in dietary fiber).

CONCLUSION: The gastric cancer screening and preventive behaviors of GCRs have yet to be improved. To increase awareness among GCRs, systematic family education programs should be implemented.

Interactions between CagA and smoking in gastric cancer

AIM: To examine the interactions between cytotoxin-associated gene (CagA) positive Helicobacter pylori infection and smoking in non-cardiac gastric cancer.

METHODS: A case-control study (257 cases and 514 frequency-matched controls) was conducted from September 2008 to July 2010 in Xi’an, China. Cases were newly diagnosed, histologically confirmed non-cardiac cancer. Controls were randomly selected from similar communities to the cases and were further matched by sex and age (± 5 years). A face-to-face interview was performed by the investigators for each participant. Data were obtained using a standardized questionnaire that included questions regarding known or suspected lifestyle and environmental risk factors of gastric cancer. A 5 mL sample of fasting venous blood was taken. CagA infection was serologically detected by enzyme-linked immunosorbent assays.

RESULTS: Smoking and CagA infection were statistically significant risk factors of non-cardiac cancer. CagA was categorized in tertiles, and the odds ratio (OR) was 12.4 (95% CI: 6.1-20.3, P = 0.003) for CagA after being adjusted for confounding factors when the high-exposure category was compared with the low-exposure category. Smokers had an OR of 5.4 compared with subjects who never smoked (95% CI: 2.3-9.0, P = 0.002). The OR of non-cardiac cancer was 3.5 (95% CI: 1.8-5.3) for non-smokers with CagA infection, 3.5 (95% CI: 1.9-5.1) for smokers without CagA infection, and 8.7 (95% CI: 5.1-11.9) for smokers with CagA infection compared with subjects without these risk factors. After adjusting for confounding factors, the corresponding ORs of non-cardiac cancer were 3.2 (95% CI: 1.5-6.8), 2.7 (95% CI: 1.3-4.9) and 19.5 (95% CI: 10.3-42.2), respectively. There was a multiplicative interaction between smoking and CagA, with a synergistic factor of 2.257 (Z = 2.315, P = 0.021).

CONCLUSION: These findings support a meaningful interaction between CagA and smoking for the risk of gastric cancer which may have implications for its early detection.

Salt intake and type of intestinal metaplasia in Helicobacter pylori-infected Portuguese men

The relation between salt intake and intestinal metaplasia (IM) types and the potential interaction with H. pylori virulence are poorly understood and may contribute to further understand gastric carcinogenesis. We quantified the association between dietary salt exposure and complete, incomplete, and mixed IM, taking into account the potential effect modification according to the virulence of H. pylori infecting strains. H. pylori-infected male volunteers (n = 233) underwent an upper digestive endoscopy and completed questionnaires comprising different measures of salt exposure (main food items/groups contributing to dietary salt intake, estimated dietary sodium intake, visual analogical scale for salt intake, preference for salty/salted foods). A histological diagnosis was assigned based on the most severe lesion observed. H. pylori virulence was assessed by characterizing vacA and cagA genes. Odds ratios were estimated through age- and education-adjusted logistic regression models. The risk of IM was not significantly increased in H. pylori infected subjects with higher levels of salt consumption. The lack of association was consistent across measures of salt exposure, categories of H. pylori virulence, and types of IM. In conclusion, in this H. pylori positive population, salt intake did not increase the risk of any IM type, regardless of the virulence of the infecting strains.

Relevance of high virulence Helicobacter pylori strains and futility of CDX2 expression for predicting intestinal metaplasia after eradication of infection

OBJECTIVE

Different Helicobacter pylori genotypes are associated with distinct inflammatory responses and consequent development of pre-neoplastic lesions, namely intestinal metaplasia (IM), which is dependent on the expression of CDX2. We aimed to evaluate IM progression/regression in the context of H. pylori eradication, bringing into play the effect of the virulence of infecting H. pylori strains and the hypothesis that CDX2 expression might be a marker for later development of IM.

MATERIAL AND METHODS

Sixty-five male volunteers were evaluated by endoscopy before H. pylori eradication and after a median six-year follow-up. Histological diagnosis was performed at baseline and follow-up, and baseline H. pylori genotypes and CDX2 expression in non-metaplastic foci were also assessed.

RESULTS

Fifty-one individuals remained free from infection at follow-up. Six out of 27 who had no metaplastic lesions at baseline developed IM. CDX2 nuclear expression was observed in 15 of the 21 cases (71.4%) showing no progression to IM, and in three out of six cases (50%) with progression to IM (p = 0.367). Six of the 24 cases with IM at baseline showed regression to less severe outcomes, which was less frequent in those infected with high-virulence strains (7.7% vs. 50%, p = 0.047). In the latter there is a significant persistence of lymphoid follicles.

CONCLUSIONS

Our results support that under infection with high virulence H. pylori strains, IM is a point of difficult return in the gastric carcinogenic pathway. The appearance of CDX-expressing cells in non-metaplastic foci was not associated with the development of IM during the six-year follow-up.

Helicobacter pylori and gastric cancer in the Middle East: A new enigma?

The Middle East is the home of ethnic groups from three main backgrounds: Semitic (Arabs and Jews), Indo-European (Persians and Kurdish) and Turkic (Turkish and Turkmens). Its geographic location, which has been under continuous influences from Asia, Europe and Africa, has made it an ideal site for epidemiological studies on Helicobacter pylori (H. pylori) infection and genotyping. The gastric cancer rate differs in this region from very high in Iran (26.1/10⁵) to low in Israel (12.5/10⁵) and very low in Egypt (3.4/10⁵). Epidemiological studies showed that the prevalence of H. pylori is almost similar in those countries with a high level of infection in childhood. Importantly, the frequency of vacA s1 and m1 regions and cagA+ genotypes were higher in non Semitic populations who inhabit the North than Semitic populations, the inhabitants of Southern parts of the Middle East. H. pylori infection prevalence, distribution pattern of virulence factors, diet and smoking could not have explained the difference in cancer rate. This reflects the multifactorial aetiology of gastric cancer and suggests that H. pylori infection does not always directly correlate with the risk for gastrointestinal disease, such as gastric cancer. Further detailed investigations and international comparative studies of each risk factor need to be performed to investigate whether this represents a true enigma.

Pathophysiology of intestinal metaplasia of the stomach: emphasis on CDX2 regulation

IM (intestinal metaplasia) of the stomach is a pre-neoplastic lesion that usually follows Helicobacter pylori infection and that confers increased risk for gastric cancer development. After setting the role played by CDX2 (Caudal-type homeobox 2) in the establishment of gastric IM, it became of foremost importance to unravel the regulatory mechanisms behind its de novo expression in the stomach. In the present paper, we review the basic pathology of gastric IM as well as the current knowledge on molecular pathways involved in CDX2 regulation in the gastric context.

Association between cytokine gene polymorphisms and gastric precancerous lesions: systematic review and meta-analysis

Polymorphisms within interleukin-1 (IL1) and tumor necrosis factor alpha (TNFA) gene clusters are associated with an increased risk of gastric cancer. However, their role in gastric precancerous lesions remains poorly understood. Our objective was to perform a meta-analysis of studies addressing the association between IL1B-511, IL1RN variable number of tandem repeat, and TNFA-308 gene polymorphisms and gastric precancerous lesions, including original data from Portugal and Mozambique. Published studies on the association between these cytokine gene polymorphisms and gastric precancerous lesions were identified by systematic review, and estimates of the association were combined using random-effects meta-analysis taking into account new data obtained from Portuguese volunteer shipyard workers (n = 215) and Mozambican dyspeptic patients (n = 96) who underwent endoscopic and pathologic evaluation following the same protocol. Odds ratio (OR) estimates for intestinal metaplasia were 2.83 [95% confidence interval (95% CI), 1.15-6.96] for the IL1RN*22 genotype, 1.86 (95% CI, 1.03-3.36) for IL1B-511 T carriers, and 0.59 (95% CI, 0.12-3.04) for the TNFA-308*AA genotype in the Portuguese sample. All Mozambican subjects with intestinal metaplasia were T carriers for IL1B-511 and none had the 2 allele for IL1RN. In meta-analysis, IL1RN*22 genotype was associated with an increased risk of gastric precancerous lesions (22 versus LL: OR, 2.27; 95% CI, 1.40-3.70; I(2) = 26.4%; 12 studies). No such association was found for the IL1B-511 (TT versus CC: OR, 1.34; 95% CI, 0.87-2.07; I(2) = 65.7%; 13 studies) or TNFA-308 genotypes (AA versus GG: OR, 0.93; 95% CI, 0.35-2.43; I(2) = 0.0%; 7 studies). The IL1RN*22 genotype seems to consistently increase the risk of gastric precancerous lesions, supporting a role for this polymorphism in the early stages of gastric carcinogenesis.

Relevance of Helicobacter pylori genotypes in gastric pathology and its association with plasma malondialdehyde and nitric oxide levels

Persistent infection with Helicobacter pylori confers an increased risk of peptic ulceration and gastric adenocarcinoma. Reactive oxygen and nitrogen species play a crucial role in the progression from normal gastric mucosa to cancer. The aim of the present study was to investigate the plasma malondialdehyde and nitric oxide levels in H. pylori related gastroduodenal diseases and associate their levels with gastric pathology and genotypes of H. pylori. Malondialdehyde and nitric oxide levels in plasma samples of 250 subjects were spectrophotometrically determined. Subsequently, genotypic and histopathological assessment was performed in gastric biopsies obtained during endoscopy. The levels of MDA and NO exceeded in subjects infected with genotype-1 of Hp than those with other genotypes suggesting more precise interaction of highly virulent strains of Hp in eliciting severe tissue damage. In conclusion, the study demonstrates close relationship between the plasma malondialdehyde and nitric oxide levels, gastric histopathology and genotypes of H. pylori.

Infection-associated FUT2 (Fucosyltransferase 2) genetic variation and impact on functionality assessed by in vivo studies

The secretor (Se)/nonsecretor (se) histo-blood group variation depends on the action of the FUT2 enzyme and has major implications for human susceptibility to infections. To characterize the functionality of FUT2 variants, we assessed the correlation between saliva phenotypes and sequence variation at the FUT2 gene in sixty seven individuals from northern Portugal. While most non-secretor haplotypes were found to carry the 428G > A nonsense mutation in association with a 739G > A missense substitution, we have also identified a recombinant haplotype carrying the 739*A allele together with the efficient 428*G variant in individuals with the Se phenotype. This finding suggested, in contrast to previous results, that the 739*A allele encodes an efficient Se allele. To test this hypothesis we evaluated the in vivo enzyme activity of full coding expression constructs in transient transfection of CHO-K1 cells using FACS (fluorescence-activated cell sorting) analysis and expression of type 2 and type 3 chain H structures as read out. We detected FUT2 activity for the 739*A expression construct, demonstrating that the 739G > A substitution is indeed not inactivating. In accordance with the hypothesis that FUT2 is under long standing balancing selection, we estimated that the time depth of FUT2 global genetic variation is as old as 3 million years. Age estimates of specific variants suggest that the 428G > A mutation occurred at least 1.87 million years ago while the 739G > A substitution is about 816,000 years old. The 385A > T missense mutation underlying the non-secretor phenotype in East Asians appears to be more recent and is likely to have occurred about 256,000 years ago.

Sensitivity is not an intrinsic property of a diagnostic test: empirical evidence from histological diagnosis of Helicobacter pylori infection

Background

We aimed to provide empirical evidence of how spectrum effects can affect the sensitivity of histological assessment of Helicobacter pylori infection, which may contribute to explain the heterogeneity in prevalence estimates across populations with expectedly similar prevalence.

Methods

Cross-sectional evaluation of dyspeptic subjects undergoing upper digestive endoscopy, including collection of biopsy specimens from the greater curvature of the antrum for assessment of H. pylori infection by histopathological study and polymerase chain reaction (PCR), from Portugal (n = 106) and Mozambique (n = 102) following the same standardized protocol.

Results

In the Portuguese sample the prevalence of infection was 95.3% by histological assessment and 98.1% by PCR. In the Mozambican sample the prevalence was 63.7% and 93.1%, respectively. Among those classified as infected by PCR, the sensitivity of histological assessment was 96.2% among the Portuguese and 66.3% among the Mozambican. Among those testing positive by both methods, 5.0% of the Portuguese and 20.6% of the Mozambican had mild density of colonization.

Conclusions

This study shows a lower sensitivity of histological assessment of H. pylori infection in Mozambican dyspeptic patients compared to the Portuguese, which may be explained by differences in the density of colonization, and may contribute to explain the heterogeneity in prevalence estimates across African settings.

High prevalence of virulent Helicobacter pylori strains in symptomatic Bulgarian patients

The aim of the study was to evaluate the prevalence of main virulence genes in Helicobacter pylori strains from 116 patients with peptic ulcers (41 cases) and nonulcer diseases (75) by polymerase chain reaction (PCR) with pure cultures and to compare the results with those by multiplex PCR in 39 H. pylori-positive gastric biopsies in another center in Sofia, Bulgaria. Strain susceptibility to amoxicillin, metronidazole, and clarithromycin was determined by agar dilution method. By PCR with pure cultures, coinfections with multiple H. pylori strains were found in 8 (6.9%) patients who were excluded from the statistical analysis. Prevalence of toxigenic type vacA s1 was higher (91.7%) than that usually reported in Europe. cagA-positive genotype was detected in most (81.5%) strains, and almost all of them harbored vacA s1 genotype. Strains with cagA+/vacA s1a genotype were more common (80.6%) than the other genotypes (19.4%, P = 0.0001). The ulcer patients had more often virulent strains than the other patients (92.3% versus 75.4% for cagA+, 100.0% versus 87.0% for vacA s1, 100% versus 84.0% for vacA s1a, and 92.3% versus 73.9% for cagA+/vacA s1a, respectively). The prevalence of H. pylori virulence-associated genes was not associated with patients' sex and age or with the antibacterial resistance of strains. The most common H. pylori genotype was cagA+/vacA s1a. Similar prevalence of cagA-positive (82.1%), vacA s1 (97.4%), and cagA+/vacA s1 strains (79.5%) was found by multiplex PCR in gastric biopsies in the 2nd center. In conclusion, H. pylori strains with virulent genotypes are widespread in symptomatic Bulgarian patients.

Prevalence of Helicobacter pylori infection, chronic gastritis, and intestinal metaplasia in Mozambican dyspeptic patients

We estimated the prevalence of Helicobacter pylori infection, chronic gastritis, atrophy, and intestinal metaplasia in dyspeptic patients from Maputo Central Hospital, Mozambique and evaluated the relationship between infection and histopathological features of chronic gastritis. Biopsies from 109 consecutive patients observed in 2005-2006 were collected from antrum, incisura angularis, and corpus for histopathological study according to the Modified Sydney system. H. pylori infection was assessed by histology and polymerase chain reaction. H. pylori prevalence was 94.5%. Chronic gastritis was the most frequent diagnosis (90.8%). Degenerative surface epithelial damage was associated with higher H. pylori density. Glandular atrophy (8.3%) and intestinal metaplasia (8.3%) were infrequent. Our results confirm previous observations in African countries with high prevalence of H. pylori infection and low rates of gastric cancer: high frequency of chronic H. pylori-associated gastritis with very low frequency of gastric atrophy and intestinal metaplasia.

Infection by Helicobacter pylori expressing the BabA adhesin is influenced by the secretor phenotype

Helicobacter pylori (Hp) infects half the world's population and causes diverse gastric lesions, from gastritis to gastric cancer. Our aim was to evaluate the significance of secretor and Lewis status in infection and in vitro adherence by Hp expressing BabA adhesin. We enrolled 304 Hp-infected individuals from Northern Portugal. Gastric biopsies, blood and saliva were collected. Polymerase chain reaction (PCR) and immunofluorescence were used to detect BabA+ Hp in gastric biopsies. In vitro adherence by a BabA expressing Hp strain to gastric biopsies was performed. Secretor status was identified by Ulex, a lectin that recognizes secretor-dependent glycan structures in saliva and in gastric mucosa, and by Lewis(a/b) antibodies, and indirectly by identification of an inactivating mutation in the FUT2 gene (G428A). BabA status of infecting Hp was associated with CagA and VacAs1 (p < 0.05), intercellular localization of Hp (p < 0.01) and the presence of intestinal metaplasia (p < 0.05) and degenerative alterations (p < 0.005) in the biopsies. BabA was associated (p < 0.05) with Ulex staining of gastric biopsies and, although not significantly, to absence of homozygosity for FUT2 G428A inactivating polymorphism. In vitro Hp adherence was higher in cases wild-type or heterozygous for FUT2 G428A mutation (p < 0.0001), cases staining for Ulex (p < 0.0001) and a(-)b+ and a(-)b(-) secretor phenotypes (p < 0.001). In conclusion, BabA+ Hp infection/adhesion is secretor-dependent and associated with the severity of gastric lesions.

Smoking and gastric cancer: systematic review and meta-analysis of cohort studies

OBJECTIVE

We conducted a systematic review of studies addressing the relation between cigarette smoking and gastric cancer to estimate the magnitude of the association for different levels of exposure and cancer locations.

METHODS

Published cohort, case-cohort, and nested case-control studies were identified through PubMed, Scopus, and Web of Science searches, from inception to July 2007. Relative risk (RR) estimates referring to the comparison of two categories of exposure (e.g., current smokers vs. never smokers) were combined using a random effects model. Generalized least squares regression was used for trend estimation. Heterogeneity was quantified using the I (2) statistic.

RESULTS

Forty-two articles were considered for the systematic review. Comparing current smokers with never smokers: the summary RR estimates were 1.62 in males (95% CI: 1.50-1.75; I (2) = 46.0%; 18 studies) and 1.20 in females (95% CI: 1.01-1.43; I (2) = 49.8%; nine studies); the RR increased from 1.3 for the lowest consumptions to 1.7 for the smoking of approximately 30 cigarettes per day in the trend estimation analysis; smoking was significantly associated with both cardia (RR = 1.87; 95% CI: 1.31-2.67; I (2) = 73.2%; nine studies) and non-cardia (RR = 1.60; 95% CI: 1.41-1.80; I (2) = 18.9%; nine studies) cancers.

CONCLUSION

Our study provides solid evidence to classify smoking as the most important behavioral risk factor for gastric cancer.