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

Burden of Gastrointestinal Tumors in Asian Countries, 1990-2021: An Analysis for the Global Burden of Disease Study 2021

Background

Gastrointestinal tumors represent a significant component of the cancer burden in Asia. This study aims to evaluate the burden of gastrointestinal tumors in Asia from 1990 to 2021 using data from the Global Burden of Disease Study 2021 (GBD 2021).

Methods

The absolute incidence, mortality, and disability adjusted life years (DALYs) number and rate of six gastrointestinal tumors(colon and rectum cancer (CRC), stomach cancer (SC), pancreatic cancer (PC), esophageal cancer (EC), liver cancer (LC) and gallbladder and biliary tract cancer (GBTC)) in 48 Asian countries were extracted from GBD 2021. Differences were analyzed based on gender, age, year, location and socio-demographic index (SDI).

Results

In 2021, SC accounted for the highest disease burden in Asia (DALYs=16.41million [95% UI: 13.70, 19.62]). From 1990 to 2021, the age-standardized incidence rates of EC, LC, and SC in Asia declined, while the incidence rates of CRC and PC increased significantly, with CRC showing the largest rise (AAPC=1.08 [95% CI: 1.02 to 1.12]). Gastrointestinal tumors DALY rates peaked at age 70 and above, with males generally exhibiting higher rates than females. Furthermore, East Asia bears a higher burden compared to other Asian subregions. A higher SDI correlates with increased DALY rates for PC, but no linear relationship was observed for other gastrointestinal tumors.

Conclusion

The burden of gastrointestinal tumors in Asia remains high and may continue to increase. Therefore, effective prevention and treatment measures are essential to address the challenge posed by gastrointestinal tumors.

Association between Helicobacter pylori and its eradication and the development of cancer

BACKGROUND

Helicobacter pylori (H. pylori) is a gram-negative gastrointestinal pathogen that colonises the human stomach and is considered a major risk factor for gastric cancer and mucosa-associated lymphoid tissue lymphoma. Furthermore, H. pylori is a potential trigger of a wide spectrum of extragastric cancer entities, extraintestinal chronic inflammatory processes and autoimmune diseases. In the present study, we evaluated the association between H. pylori infection and its eradication with the development of subsequent gastrointestinal and non-gastrointestinal cancer.

METHODS

We identified 25 317 individuals with and 25 317 matched individuals without a diagnosis of H. pylori from the Disease Analyzer database (IQVIA). A subsequent cancer diagnosis was analysed using Kaplan-Meier and conditional Cox-regression analysis as a function of H. pylori and its eradication.

RESULTS

After 10 years of follow-up, 12.8% of the H. pylori cohort and 11.8% of the non-H. pylori cohort were diagnosed with cancer (p=0.002). Results were confirmed in regression analysis (HR: 1.11; 95% CI 1.04 to 1.18). Moreover, a non-eradicated H. pylori status (HR: 1.18; 95% CI 1.07 to 1.30) but not an eradicated H. pylori status (HR: 1.06; 95% CI 0.97 to 1.15) was associated with a subsequent diagnosis of cancer. In subgroup analyses, H. pylori eradication was negatively associated with bronchus and lung cancer (HR: 0.60; 95% CI 0.44 to 0.83).

CONCLUSION

Our data from a large outpatient cohort in Germany reveal a distinct association between H. pylori infection and the subsequent development of cancer. These data might help to identify patients at risk and support eradication strategies in the future.

Immunohistochemical Expression of CD90, CD133, and TPM1 in Relation to Gastric Cancer and H. pylori Association

BACKGROUND

Gastric cancer (GC) is the second most common cause of cancer-related death worldwide. Multiple malignancies overexpress CD90, making it a helpful diagnostic and prognostic marker. CD133 is suggested to be related to poor prognosis in GC. Tropomyosin-1 (TPM1) tumor-suppressor gene low expression may predict poor survival in GC. Our study aimed to investigate CD90, CD133, and TPM1 immunohistochemical expression in GC in relation to diagnosis, prognosis, and Helicobacter pylori (H. pylori) infection.

METHODS

144 paraffin blocks containing gastric cancerous (108 cases), and non-cancerous (36 cases) tissue were analyzed histopathologically for the type of lesion, grade, and stage of malignancy and by using an immunohistochemical assay for studying the expression of CD90, CD133, and TPM1. Data analysis was carried out using the Statistical Package for the Social Sciences (SPSS) version 20.0.

RESULTS

The obtained results showed a significantly higher expression of CD90 and CD133 while showing a significantly lower expression of TPM1 in malignant samples compared to benign ones. CD90 was significantly higher in grade-3, stage-3, and N3 (p<0.05), with no significant difference concerning positive and negative H. pylori samples. CD133 percentage and H-score were significantly higher in grade-2 and stage-4 tumors than in other grades and stages, while being insignificantly higher in N3 and H. pylori-positive cases. TPM1 expression levels were significantly downregulated in GC and H. pylori-positive cases (p<0.05). TPM1 downregulation was associated with grade progression, increased depth of invasion, and tumor node metastasis.

CONCLUSION

CD90, CD133, and TPM1 immunohistochemical expression in the gastric biopsy are related firmly to grades and stages of GC as well as H. pylori infection, so they could be of prognostic value. Further studies on a larger sample size are recommended.

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

BACKGROUND & AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Population Attributable Fraction of Helicobacter pylori Infection-Related Gastric Cancer in Korea: A Meta-Analysis

PURPOSE

This study aimed to determine the proportion of gastric cancer attributable to Helicobactor pylori in the Korean population. Infection with H. pylori has been recognized as the most significant risk factor for gastric cancer. In Korea, gastric cancer is the most common cancer that accounted for 13.3% of all cancers in 2016. In particular, men are most commonly diagnosed with gastric cancer; the age-standardized incidence rate in men is 49.6 per 100,000, which is more than twice the incidence in women.

MATERIALS AND METHODS

The population attributable fraction (PAF) was calculated as a function of the relative risk (RR) of gastric cancer associated with H. pylori infections. To estimate PAF of gastric cancer due to H. pylori, the prevalence of H. pylori infections was extrapolated for the year of 1990 and a pooled RR was obtained by conducting a meta-analysis of studies recently published in Korea.

RESULTS

The estimated prevalence of H. pylori was 76.4% in men and 71.9% in women. The RRs (95% confidence interval) pooled from case-control studies using a random effects model was 1.69 (1.29-2.22) for overall gastric cancer and 2.17 (1.04-4.55) for non-cardia gastric cancer. Using the RR for overall gastric cancer, the estimated PAFs due to H. pylori were 34.5% in men and 33.2% in women.

CONCLUSION

The occurrence of gastric cancer in Koreans may be affected by other risk factors in addition to H. pylori infection, which may contribute to increasing baseline risk for gastric cancer.

Disaggregated mortality from gastrointestinal cancers in Asian Americans: Analysis of United States death records

Asian Americans (AAs) are heterogeneous, and aggregation of diverse AA populations in national reporting may mask high-risk groups. Gastrointestinal (GI) cancers constitute one-third of global cancer mortality, and an improved understanding of GI cancer mortality by disaggregated AA subgroups may inform future primary and secondary prevention strategies. Using national mortality records from the United States from 2003 to 2017, we report age-standardized mortality rates, standardized mortality ratios and annual percent change trends from GI cancers (esophageal, gastric, colorectal, liver and pancreatic) for the six largest AA subgroups (Asian Indians, Chinese, Filipinos, Japanese, Koreans and Vietnamese). Non-Hispanic Whites (NHWs) are used as the reference population. We found that mortality from GI cancers demonstrated nearly 3-fold difference between the highest (Koreans, 61 per 100 000 person-years) and lowest (Asian Indians, 21 per 100 000 person-years) subgroups. The distribution of GI cancer mortality demonstrates high variability between subgroups, with Korean Americans demonstrating high mortality from gastric cancer (16 per 100 000), and Vietnamese Americans demonstrating high mortality from liver cancer (19 per 100 000). Divergent temporal trends emerged, such as increasing liver cancer burden in Vietnamese Americans, which exacerbated existing mortality differences. There exist striking differences in the mortality burden of GI cancers by disaggregated AA subgroups. These data highlight the need for disaggregated data reporting, and the importance of race-specific and personalized strategies of screening and prevention.

Antioxidant-Rich Diet, GSTP1 rs1871042 Polymorphism, and Gastric Cancer Risk in a Hospital-Based Case-Control Study

Background

Chronic gastritis along with Helicobacter pylori (H. pylori) infection has been implicated in inflammatory response-related genes linked to the causation of gastric cancer. Glutathione S-transferase Pi (GSTP1) plays a role in regulating oxidative stress and detoxification against carcinogenesis. In this study, we aimed to determine whether an antioxidant-rich diet is associated with gastric cancer risk and identify how this association could be altered by GSTP1 genetic variants.

Methods

This study included 1,245 participants (415 cases and 830 controls) matched for age and sex. The dietary antioxidant capacity was estimated based on the oxygen radical absorbance capacity (ORAC) incorporated with a semiquantitative food frequency questionnaire. Five single nucleotide polymorphisms (SNPs) of GSTP1 (rs1695, rs749174, rs1871042, rs4891, and rs947895) were selected among the exome array genotype data.

Results

High dietary ORAC was inversely associated with gastric cancer (hydrophilic ORAC OR _{T3vs. T1}, 95% CI = 0.57, 0.39–0.82, P = 0.004; lipophilic ORAC = 0.66, 0.45–0.95, P = 0.021; total phenolics = 0.57, 0.39–0.83, P = 0.005). The polymorphism rs1871042 increased the risk of gastric cancer (OR, 95% CI = 1.55, 1.10–2.16, P = 0.01, CT+TT vs. CC). A remarkably reduced risk of gastric cancer was observed among those who had a high dietary ORAC according to rs1871042 polymorphism (hydrophilic ORAC OR _{T3vs. T1}, 95% CI = 0.36, 0.17–0.78, P for trend = 0.013; lipophilic ORAC = 0.58, 0.37–0.93, P for trend = 0.021; total phenolics = 0.38, 0.17–0.83, P for trend = 0.019).

Conclusions

Our findings indicate that dietary ORAC intake may be inversely associated with the risk of gastric cancer altered by genetic variants of GSTP1, providing new intervention strategies for gastric cancer patients.

Unraveling the identity of gastric cardiac cancer

The classification of gastric cardiac carcinoma (GCC) is controversial. It is currently grouped with esophageal adenocarcinoma (EAC) as an adenocarcinoma of the gastroesophageal junction (GEJ). Recently, diagnostic criteria for adenocarcinoma in the GEJ were established and GCC was separated from EAC. We viewed published evidence to clarify the GCC entity for better patient management. GCC arises in the cardiac mucosa located from 3 cm below and 2 cm above the GEJ line. Compared with EAC, GCC is more like gastric cancer and affects a higher proportion of female patients, younger patients, those with a lower propensity for reflux disease, a wider histopathologic spectrum, and more complex genomic profiles. Although GCC pathogenesis mechanisms remain unknown, the two-etiology proposal is appealing: in high-risk regions, the Correa pathway with Helicobacter pylori infection, chronic inflammation, low acid and intestinal metaplasia, dysplasia and carcinoma may apply, while in low-risk regions the sequence from reflux toxin-induced mucosal injury and high acid, to intestinal metaplasia, dysplasia and carcinoma may occur. In early GCC a minimal risk of nodal metastasis argues for a role of endoscopic therapy, whereas in advanced GCC, gastric cancer staging rules and treatment strategy appear to be more appropriate than the esophageal cancer staging scheme and therapy for better prognosis stratification and treatment. In this brief review we share recent insights into the epidemiology, histopathology and genetics of GCC and hope that this will stimulate further investigations in order to improve the clinical management of patients with GCC.

Association Between ALDH2 Polymorphism and Gastric Cancer Risk in Terms of Alcohol Consumption: A Meta-Analysis

BACKGROUND

Alcohol may increase gastric cancer risk. Alcohol can be more carcinogenic in persons who possess inactive ALDH2. The aim of this meta-analysis was to evaluate whether ALDH2 polymorphism can affect alcohol-induced gastric carcinogenesis.

METHODS

We searched the PubMed, EMBASE, and Cochrane databases to identify relevant articles published between January 2000 and September 2019. Eligible articles were selected according to inclusion and exclusion criteria. The data were analyzed using Review Manager 5.3.

RESULTS

A total of 7 case-control studies on ALDH2 rs671 polymorphism consisting of 3,251 gastric cancer cases and 4,943 controls were included in the analysis. Inactive ALDH2 genotypes (G/A or A/A) were associated with an increased risk of gastric cancer (odds ratio [OR] = 1.26, 95% confidence interval [CI]: 1.04 to 1.52, p = 0.02, I²  = 64%), compared with active ALDH2 (G/G genotype). Subgroup analysis by alcohol consumption showed that inactive ALDH2 increased risk for gastric cancer in moderate to heavy drinkers (OR = 1.85, 95% CI: 1.52 to 2.25, p < 0.01, I² = 6%) more than in nondrinkers or mild drinkers (OR = 1.19; 95% CI: 1.05 to 1.36, p < 0.01, I²  = 6%). Moderate/heavy alcohol consumption increased gastric cancer risk in individuals with inactive ALDH2 (OR = 2.23, 95% CI: 1.63 to 3.05, p < 0.01, I² = 30%) more than those with active ALDH2 (OR = 1.40, 95% CI: 0.98 to 2.01, p = 0.07, I² = 85%).

CONCLUSIONS

The ALDH2 polymorphism modifies the risk of gastric cancer. Moderate/heavy drinkers are more susceptible to gastric cancer than non-drinkers or light drinkers with inactive ALDH2.

Impact of previous metronidazole exposure on metronidazole-based second-line quadruple therapy for Helicobacter pylori infection

BACKGROUND/AIMS

The negative effects on the eradication success of Helicobacter pylori infection after previous exposure to macrolides, including clarithromycin on clarithromycin-based first-line therapy have been demonstrated. However, whether this is true for metronidazole-based second-line quadruple therapy remains unclear. We investigated the relationship between past administration of metronidazole and the failure of metronidazole-based second-line quadruple therapy in patients with H. pylori infection.

METHODS

Patients over 20 years of age who were diagnosed with H. pylori infection between January 1998 and March 2016 were enrolled in this study. The relationship between the clinical parameters and the results of a C13-urea breath test after metronidazole-based second-line quadruple therapy was analyzed in patients for whom clarithromycin-based triple therapy failed to eradicate H. pylori.

RESULTS

The H. pylori eradication failure rate was significantly higher in patients with a history of metronidazole use than in patients without a history of metronidazole use (p = 0.011). Multivariable analysis showed that the odds ratio of previous metronidazole use for eradication failure was 3.468 (95% confidence interval, 1.391 to 8.649; p = 0.008). In the subgroup analysis of patients with a history of metronidazole use, the duration of metronidazole use and interval between its use and eradication therapy did not significantly affect H. pylori eradication failure.

CONCLUSION

Previous exposure to metronidazole was a significant risk factor for treatment failure of metronidazole-based second-line quadruple therapy; therefore, this should be considered when establishing a treatment strategy for patients with H. pylori infection.

The Utility of Gastrointestinal Endoscopic Examination Versus Positron Emission Tomography-Computed Tomography in the Detection of Second Primary Lesions in Korean Patients With Head and Neck Cancer

OBJECTIVE

Head and neck cancer often accompany a synchronous secondary primary lesion in the digestive tract. The aim of this study was to compare detection rates between positron emission tomography-computed tomography (PET-CT) and esophagogastroduodenoscopy (G-fiber) or colonoscopy (C-fiber) in the initial staging and to analyze risk factors for premalignant, malignant, and total synchronous secondary primary lesions.

METHODS

A total of 739 patients with head and neck cancer who underwent PET-CT, G-fiber, or C-fiber were analyzed retrospectively.

RESULTS

Positron emission tomography-CT did not definitely detect any premalignant synchronous secondary primary lesions (0 [0%] of 739) but definitely detected 10 malignant synchronous secondary primary lesions (10 [1.35%] of 739). Esophagogastroduodenoscopy or C-fiber detected all 20 premalignant synchronous secondary primary lesions (20 [2.71%] of 739) and all 37 malignant synchronous secondary primary lesions (37 [5.00%] of 739). The patients with nasopharynx cancer tended to have premalignant synchronous secondary primary lesions (odds ratio [OR]: 3.793; 95% CI: 1.414-10.171; P = .008). Those with distant metastasis tended to have premalignant (OR: 4.743; 95% CI: 1.508-14.916; P = .009), malignant (OR: 3.803; 95% CI: 1.486-9.731; P = .005), and total synchronous secondary primary lesions (OR: 2.753; 95% CI: 1.159-6.538; P = .022).

CONCLUSIONS

Premalignant or malignant synchronous secondary primary lesions that were not definitely detected by PET-CT could be found in the endoscopic examination.

Vitamin D Status and Gastric Cancer: A Cross-Sectional Study in Koreans

Sufficient vitamin D levels are associated with reduced Helicobacter pylori infections, which can cause gastric carcinogenesis. We examined associations between vitamin D concentrations and gastric cancer (GC) prevalence in a Korean population. We analyzed data of 33,119 adults using serum 25-hydroxyvitamin D (25(OH)D) concentrations as a biomarker of vitamin D status. Participants were classified with GC if previously diagnosed as such by a physician. After controlling for age, sex and body mass index (model A), odds ratio (OR) for GC was 0.81 (95% confidence interval [CI]: 0.70, 0.95), with a 5-ng/mL increment in total 25(OH)D concentrations. In fully adjusted models (model B), the OR for GC was 0.84 (95% CI: 0.72, 0.98), with a 5-ng/mL increment in total vitamin D. Following the classification of vitamin D concentrations into three categories or for GC in model A was 0.52 (95% CI: 0.30, 0.92) comparing between higher (≥20 ng/mL) and lower (<12 ng/mL) total 25(OH)D concentrations. In model B OR for GC was 0.57 (95% CI: 0.32, 1.00) comparing between higher and lower total 25(OH)D concentrations. Our results suggested that high vitamin D concentration was associated with lower ORs of GC in Korean adults.

Helicobacter pylori Is Associated With Precancerous and Cancerous Lesions of the Gastric Cardia Mucosa: Results of a Large Population-Based Study in China

Background: Helicobacter pylori (H. pylori) is widely accepted to be the most important cause of gastric non-cardia adenocarcinoma (GNCA), while its role in the development of gastric cardia adenocarcinoma (GCA) is not well-defined. We aimed to investigate current H. pylori infection in relation to the severity of both precancerous and cancerous lesions of the gastric cardia in an Asian population at high risk of GCA. Methods: A population-based cross-sectional study was conducted in Linzhou County, Henan Province, China. Two thousand three (2,003) randomly selected participants with data on current H. pylori infection, assayed by 13C-urea breath test (13C-UBT), and a sequence of histological diagnoses of the gastric cardia mucosa were analyzed. Results: Of 2,003 subjects, 828 (41.33%) were currently infected with H. pylori. The prevalence of current H. pylori infection increased with increasing severity of histological lesions, from 34.12% in subjects with normal gastric cardia mucosa to 52.17% in subjects with gastric cardia high-grade intraepithelial neoplasia (CHIN)/ gastric cardia adenocarcinoma (GCA) (P for trend <0.001). With H. pylori-negative subjects as the reference category, H. pylori-positive subjects had statistically significant elevated adjusted prevalence odds ratios (PORs) for each of the histological lesions. The PORs (95% CI) were 2.15 (1.74-2.64), 3.46 (2.08-5.75), 2.78 (1.90-4.07), and 3.05 (1.30-7.17) for subjects with carditis, cardia intestinal metaplasia (CIM), cardia low-grade intraepithelial neoplasia (CLIN), and CHIN/GCA), respectively. The associations remained when subjects with abnormal stomach non-cardia mucosa were excluded. Conclusions: This large epidemiologic study demonstrates a positive association between current H. pylori infection and the severity of both precancerous and cancerous lesions of the gastric cardia in an Asian population at high risk of GCA. These findings suggest that H. pylori infection may play a role throughout both early- and late-stage development of GCA.

Cathepsin S as a target in gastric cancer

Cathepsin S (Cat S) is a protein expressed in some epithelial cells, which appears to be associated with cancer metastasis and recurrence. The abnormal expression of Cat S has been reported to be associated with the progression of certain types of gastrointestinal neoplasms, including gastric cancer (GC). There is a need to identify novel biomarkers and therapeutic targets associated with the growth, invasion and migration of GC cells, in order to develop non-invasive diagnostic and prognostic procedures and design new therapeutic approaches. The aim of the present study was to assess the association between Cat S and oncogenic processes implicated in the development of GC, focusing on the diagnostic and therapeutic potential of this molecule in GC. A search was conducted through the PubMed and Cochrane Central Register of Controlled Trials electronic databases for relevant literature published between 2003 and 2018, using the mesh terms 'cathepsin S' and 'cancer' and 'gastric cancer'.

Risk of malignancy in patients with psoriasis: a 15-year nationwide population-based prospective cohort study in Korea

BACKGROUND

The association between psoriasis and risk of malignancy has not been thoroughly evaluated in a large longitudinal cohort of Asian population.

OBJECTIVE

To determine the long-term risk of malignancy in Korean adult patients with psoriasis.

METHODS

We conducted a nationwide population-based prospective cohort study with a 15-year observational period. During the baseline period (1997-2000), total 1 773 786 Korean subjects who received health insurance from the National Health Insurance System were enrolled and 5788 subjects were defined as a psoriasis group. The number of new-onset malignancy was collected during the observational period (2001-2015).

RESULTS

Patients with psoriasis had a higher adjusted hazard ratio (aHR) for development of overall malignancy [aHR 1.08, 95% confidence interval (CI) 1.00-1.18] and gastric cancer (aHR 1.31, 95% CI 1.08-1.58) compared to controls. The risks of non-Hodgkin lymphoma and non-melanoma skin cancer were significantly increased only in patients with psoriasis who received systemic treatments (aHR 2.86, 95% CI 1.07-7.61 and aHR 3.93, 95% CI 1.47-10.47, respectively).

CONCLUSION

Psoriasis is associated with long-term risk for overall malignancy in Koreans, which was primarily driven by the increased risk of gastric cancer.

Smoking status and subsequent gastric cancer risk in men compared with women: a meta-analysis of prospective observational studies

Background

Smoking is one of the well-established risk factors for gastric cancer incidence, yet whether men are more or equally susceptible to gastric cancer due to smoking compared with women is a matter of controversy. The aim of this study was to investigate and compare the effect of sex on gastric cancer risk associated with smoking.

Methods

We conducted a systemic literature search in MEDLINE, EMBASE, and the Cochrane CENTRAL databases to identify studies published from inception to December 2018. We included prospective observational studies which reported effect estimates with 95% confidence intervals (CIs) for associations of current or former smokers with the incidence of gastric cancer by sex. We calculated the ratio of relative risk (RRR) with corresponding 95% CI based on sex-specific effect estimates for current or former smokers versus non-smokers on the risk of gastric cancer.

Results

We included 10 prospective studies with 3,381,345 participants in our analysis. Overall, the summary RRR (male to female) for gastric cancer risk in current smokers was significantly increased compared with non-smokers (RRR: 1.30; 95% CI: 1.05–1.63; P = 0.019). Furthermore, there was no significant sex difference for the association between former smokers and gastric cancer risk (RRR: 1.20; 95% CI: 0.92–1.55; P = 0.178). However, the result of sensitivity analysis indicated the pooled result was not stable, which was altered by excluding a nested case-control study (RRR: 1.31; 95% CI: 1.10–1.57; P = 0.002).

Conclusion

This systematic review showed a potential sex difference association between current smokers and the risk of gastric cancer. The sex differential in smokers can give important clues for the etiology of gastric cancers and should be examined in further studies.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5601-9) contains supplementary material, which is available to authorized users.

Comparative analysis of the Hom family of outer membrane proteins in isolates from two geographically distinct regions: The United States and South Korea

BACKGROUND

Helicobacter pylori encodes numerous outer membrane proteins (OMPs), but only a few have been characterized in depth. Deletion, duplication, and allelic variation of many of the H. pylori OMPs have been reported, which suggests that these proteins may play key roles in host adaptation. Herein, we characterize the variation observed within the Hom family of OMPs in H. pylori obtained from two geographically distinct populations.

MATERIALS AND METHODS

PCR genotyping of the hom genes was carried out using clinical isolates from South Korea and the United States. A combination of statistical, phylogenetic, and protein modeling analyses was conducted to further characterize the hom variants.

RESULTS

Variations in the closely related hom genes, homA and homB, occur in regions that are predicted to encode environmentally exposed loops. A similar phenomenon is true for homC^S as compared to homC^L . Conversely, little variation was observed in homD. Certain variants of the Hom family of proteins were more prominent in isolates from the Korean population as compared to isolates from the United States.

CONCLUSION

En masse, our data show that the homA, homB, and homC profiles vary based upon the geographic origin of the strain; however, the fourth member of the hom family, homD, is more highly conserved. Additionally, protein topology modeling showed that many of the less well-conserved regions between homA and homB and between homC^S and homC^L corresponded to predicted environmentally exposed loops, suggesting that the divergence of the Hom family may be due to host adaptation/pressure.

Environmental contributions to gastrointestinal and liver cancer in the Asia-Pacific region

In the Asia-Pacific region, gastric, colorectal, and hepatocellular (liver) cancer show substantial regional variation in incidence consistent with the presence of important environmental factors. For gastric cancer, global incidence is concentrated in Asia with substantially higher rates in East Asia than in South-East Asia and Australia. The differences in incidence rates for gastric cancer in the Asia-Pacific region may be due, in part, to differences in the prevalence of Helicobacter pylori infection and the prevalence of H. pylori virulence factors. Smoking is also correlated with gastric cancer risk and is responsible for the highest population attributable fraction among men in East Asia. Colorectal cancer has increased rapidly in incidence to become the third most common digestive cancer in Asia. According to cohort studies in Asia, smoking, alcohol use, obesity, and physical inactivity increase the risk of colorectal cancer. Unlike West Asia, East Asia and Australia have high incidence rates for colorectal cancer that correlates to a high Human Development Index and a high prevalence of alcohol consumption and obesity. Liver cancer is the second most common digestive cancer in Asia. The high incidence of liver cancer in East Asia and South-East Asia is concordant with the high prevalence of hepatitis B virus and hepatitis C virus infection. Other important risk factors include alcohol use, smoking, and diabetes. The identification of the earlier and other environmental factors (currently under investigation) is central to the development and implementation of effective cancer control programs for the region.

Family history of gastric cancer is associated with the risk of colorectal neoplasia in Korean population

BACKGROUND

Family history of cancers at different sites except for colorectum has not been evaluated as a risk factor for colorectal neoplasia (CRN).

AIMS

To investigate CRN risk according to family history of cancers at 12 different sites, including stomach and colorectum.

METHODS

A cross-sectional study was performed on 139,497 asymptomatic Koreans who underwent colonoscopy as part of a health check-up.

RESULTS

The mean age of the study population was 41.6 and the prevalence of CRN was 16.3%. Multivariate analyses revealed that family histories of CRC (adjusted odds ratio; confidence interval, 1.26; 1.17-1.35) and gastric cancer (1.07; 1.01-1.13) were independent risk factors for CRN. Notably, the risk of CRN increased even more for participants with family histories of both CRC and gastric cancer (1.38; 1.12-1.70). Family history of CRC was associated with risk of CRN in participants aged both <50 and ≥50 years, whereas family history of gastric cancer was associated with risk of CRN in participants aged <50 years (1.22; 1.14-1.30), but not in participants aged ≥50 years (1.08; 0.99-1.18).

CONCLUSIONS

Family history of gastric cancer was an independent risk factor for CRN, especially in those aged <50years. Persons with family histories of gastric cancer and CRC, especially those with family histories of both, may need to begin colonoscopy earlier.

Association between alcohol consumption and the risk of gastric cancer: a meta-analysis of prospective cohort studies

Alcohol consumption is inconsistently associated with the risk of gastric cancer morbidity and mortality. The aim of this study was to systematically evaluate the association between alcohol consumption on gastric cancer risk. The PubMed, Embase, and Cochrane Library databases were searched from inception through April 2017. Prospective cohort studies evaluating the association between alcohol consumption and risk of gastric cancer which report its effect estimates with 95% confidence intervals (CIs) were included. The results summary was performed using the random-effect model. Twenty-two cohort studies involving 22,545 cases of gastric cancer and 5,820,431 participants were identified and included in our data analysis. Overall, drinking had little or no effect on gastric cancer as compared with non-drinkers. Furthermore, light and moderate alcohol consumption had no significant effect on gastric cancer risk when compared with non-drinkers. However, heavy alcohol consumption was associated with a greater risk of gastric cancer when compared with non-drinkers. The findings of the subgroup analyses indicated that light alcohol consumption was associated with a lower risk of gastric cancer in women, while heavy alcohol consumption was associated with an increased risk of gastric cancer regardless of country, gender, whether the study reported gastric cancer incidence, or whether the study adjusted for body mass index, educational attainment, or physical activity. The findings of this study suggest that light alcohol consumption might play a protective effect on gastric cancer in women, while heavy alcohol consumption is associated with a significantly increased risk of gastric cancer in all subgroups.