Helicobacter pylori serology in patients with gastric carcinoma

Rapid Detection of Helicobacter pylori by the Naked Eye Using DNA Aptamers

Helicobacter pylori was first isolated from gastritis patients by Barry J. Marshall and J. Robin Warren in 1982, and more than 90% of duodenal ulcers and about 80% of gastric ulcers are caused by H. pylori infection. Most detection methods require sophisticated instruments and professional operators, making detection slow and expensive. Therefore, it is critical to develop a simple, fast, highly specific, and practical strategy for the detection of H. pylori. In this study, we used H. pylori as a target to select unique aptamers that can be used for the detection of H. pylori. In our study, we used random ssDNA as an initial library to screen nucleic acid aptamers for H. pylori. We used binding rate and the fluorescence intensity to identify candidate aptamers. One DNA aptamer, named HPA-2, was discovered through six rounds of positive selection and three rounds of negative selection, and it had the highest affinity constant of all aptamers tested (K _d = 19.3 ± 3.2 nM). This aptamer could be used to detect H. pylori and showed no specificity for other bacteria. Moreover, we developed a new sensor to detect H. pylori with the naked eye for 5 min using illumination from a hand-held flashlight. Our study provides a framework for the development of other aptamer-based methods for the rapid detection of pathogenic bacteria.

Effect of Helicobacter pylori eradication on incidence of gastric cancer in human and animal models: underlying biochemical and molecular events

BACKGROUND

Gastric cancer remains one of the most common cancers worldwide. A strong association exists between Helicobacter pylori infection and the risk of developing noncardia gastric cancer. H. pylori eradication by antibiotic treatment is regarded as a primary chemoprevention strategy to reduce gastric cancer incidence.

AIM

To analyze the efficacy of H. pylori eradication in preventing gastric cancer in human and animal models, and to discuss whether biochemical, genetic, and epigenetic changes associated with H. pylori infection are reversible after curing the infection.

RESULTS

Several intervention trials have indicated that in some patients, H. pylori eradication leads to regression and prevents the progression of precancerous lesions. The eradication therapy reduces gastric cancer incidence in patients without any precancerous lesions at the baseline and is most effective before the development of atrophic gastritis. A few recent intervention studies in Japan have demonstrated significant prophylactic effects of eradication therapy on the development of gastric cancer, suggesting the use of eradication therapy in high-risk populations as a gastric cancer reduction strategy. However, gastric cancer may still develop despite successful eradication therapy. Studies in animal models have confirmed the use of eradication therapy at an early point of infection to prevent gastric cancer development.

CONCLUSION

H. pylori eradication may not completely abolish the risk of gastric cancer. However, eradication therapy may be used in high-risk populations to reduce gastric cancer incidence. It can reverse many biochemical, genetic, and epigenetic changes that H. pylori infection induces in the stomach.

Diet, H pylori infection and gastric cancer: evidence and controversies

Despite decreasing incidence and mortality rates, gastric cancer (GC) still remains the fourth most common cancer and the second most common cause of cancer-related deaths worldwide. Due to the limited treatment options, at present, prevention is likely to be the only effective means of controlling this disease. The success of a prevention strategy depends upon the understanding of etiological and pathogenic mechanisms underlying gastric carcinogenesis. The etiology of GC is multi-factorial, however, in the recent years, mounting evidence suggests that environmental factors play a key role. The most important environmental factors implicated in the pathogenesis of GC are diet and H pylori infection. Thus, modifications in lifestyle and dietary habit associated with eradication of H pylori infection could hypothetically represent the most promising potential targets for GC prevention. In this review we will address the evidence and the controversies on the role of these agents in non-cardia GC by focusing on retrospective and prospective observational studies and interventional trials.

[Prevalence of Helicobacter pylori infection and gastric cancer precursor lesions in patients with dyspepsia]

BACKGROUND

Helicobacter pylori infection has been considered to play significant role in gastric carcinogenesis, but only a minority of people who harbor this organism will develop gastric cancer. H. pylori infection first causes chronic non atrophic gastritis. Chronic non atrophic gastritis may evolve to atrophic gastritis and intestinal metaplasia and finally to dysplasia and adenocarcinoma.

AIMS

To estimate the prevalence of H. pylori infection and the precancerous gastric lesions and their relationship, in patients with dyspeptic symptoms who underwent upper gastrointestinal endoscopy at a reference center in the central region of Rio Grande do Sul state, Brazil.

METHODS

We analyzed gastric biopsies taken from corpus and antrum of patients who underwent upper gastrointestinal endoscopy for H. pylori detection, between 1994 and 2003. According to Sydney system, chronic non atrophic gastritis, atrophic gastritis and intestinal metaplasia were diagnosed by histological examination (H-E stain). The histological diagnoses were related to H. pylori infection status.

RESULTS

Biopsies from 2,019 patients were included in the study. Patients mean age was 52 (+/-15) and 59% were female. Seventy six percent had H. pylori infection. Normal mucosa, chronic non atrophic gastritis, atrophic gastritis and intestinal metaplasia were diagnosed in 5%, 77%, 3% and 15%, respectively. The OR for any degree of gastric mucosa lesion in infected patients was 10 (CI95% 6.50 - 17%). The OR for infected patients had chronic non atrophic gastritis was 3 (CI95% 2,2 - 3,4). The OR for infected patients had atrophic gastritis or intestinal metaplasia was less than 1.

CONCLUSIONS

The prevalence of H. pylori infection in this population was high (76%) and infected individuals had the probability 10 folds greater than non infected individuals to have any lesion of gastric mucosa. The prevalence of precancerous lesions was 77% for non atrophic chronic gastritis, 3% for atrophic gastritis and 15% for intestinal metaplasia. Infected patients had risk 3 folds greater than non-infected for the occurrence of non atrophic chronic gastritis. H. pylori infection did not show risk for occurrence of atrophic gastritis and intestinal metaplasia, suggesting that other risk factors should be involved in the carcinogenesis process.

Helicobacter pylori infection causes gastric cancer? A review of the epidemiological, meta-analytic, and experimental evidence

Since the discovery of Campylobacter-like organisms Helicobacter pylori (H pylori) more than two decades ago the possibility of a relationship with gastric cancer has been postulated, tested and supposedly proven. There have been numerous human studies of various designs from many countries around the world. Several meta-analyses have been published and more recently a small number of experimental animal studies were reported looking at the association between H pylori infection and gastric cancer. Over the years, the human epidemiological studies have produced conflicting results; the meta-analyses have as one would expect produced similar pooled estimates; while the early experimental animal studies require replication. The exact mechanisms by which H pylori might cause gastric cancer are still under investigation and remain to be elucidated.

Prevalence of Helicobacter pylori infection and intestinal metaplasia in subjects who had undergone surgery for gastric adenocarcinoma in Northwest Italy

AIM

To investigate the seroprevalence of Helicobacter pylori (H pylori) infection and its more virulent strains as well as the correlation with the histologic features among patients who had undergone surgery for gastric cancer (GC).

METHODS

Samples from 317 (184 males, 133 females, mean age 69+/-3.4 years) consecutive patients who had undergone surgery for gastric non-cardia adenocarcinoma were included in the study. Five hundred and fifty-five (294 males, 261 females, mean age 57.3+/-4.1 years) patients consecutively admitted to the Emergency Care Unit served as control. Histological examination of tumor, lymph nodes and other tissues obtained at the time of surgery represented the diagnostic "gold standard". An enzyme immunosorbent assay was used to detect serum anti-H pylori (IgG) antibodies and Western blotting technique was utilized to search for anti-CagA protein (IgG).

RESULTS

Two hundred and sixty-one of three hundred and seventeen (82.3%) GC patients and 314/555 (56.5%) controls were seropositive for anti-H pylori (P<0.0001; OR, 3.58; 95%CI, 2.53-5.07). Out of the 317 cases, 267 (84.2%) were seropositive for anti-CagA antibody vs 100 out of 555 (18%) controls (P<0.0001; OR, 24.30; 95%CI, 16.5-35.9). There was no difference between the frequency of H pylori in intestinal type carcinoma (76.2%) and diffuse type cancer (78.8%). Intestinal metaplasia (IM) was more frequent but not significant in the intestinal type cancer (83.4% vs 75.2% in diffuse type and 72.5% in mixed type). Among the patients examined for IM, 39.8% had IM type I, 8.3% type II and 51.9% type III(type III vs others, P = 0.4).

CONCLUSION

This study confirms a high seroprevalence of H pylori infection in patients suffering from gastric adenocarcinoma and provides further evidence that searching for CagA status over H pylori infection might confer additional benefit in identifying populations at greater risk for this tumor.

Detection of serum anti-Helicobacter pylori immunoglobulin G in patients with different digestive malignant tumors

AIM: To investigate the seroprevalence of Helicobacter pylori infection in patients with different digestive malignant tumors.

METHODS: Enzyme linked immunosorbent assay (ELISA) was used to detect serum anti-Helicobacter pylori IgG antibody in 374 patients with different digestive malignant tumors and 310 healthy subjects (normal control group).

RESULTS: The seroprevalence of Helicobacter pylori infection was 61.50% (230/374) and 46.77% (145/310), respectively, in patients with digestive tumors and normal controls (P < 0.05). The seroprevalence was 52.38% (33/63), 86.60% (84/97), 83.14% (84/101), 45.24 (19/42), 51.13% (18/35) and 44.44% (16/36), respectively in patients with carcinomas of esophagus, stomach, duodenum, rectum, colon and liver (P < 0.01). In patients with intestinal and diffuse type gastric cancers, the seroprevalence was 93.75% (60/64) and 72.73% (24/33), respectively (P < 0.05). In patients with gastric antral and cardiac cancers, the seroprevalence was 96.43% (54/56) and 73.17% (30/41), respectively (P < 0.05). In patients with ulcerous and proliferous type duodenal cancers, the seroprevalence of H. pylori infection was 91.04% (61/67) and 52.27% (23/44), respectively (P < 0.05). In patients with duodenal bulb and descending cancers, the seroprevalence was 94.20% (65/69) and 45.20% (19/42), respectively (P < 0.05).

CONCLUSION: H. pylori infection is associated with occurrence and development of gastric and duodenal carcinomas. Furthermore, it is also associated with histological type and locations of gastric and duodenal carcinomas.

Review article: test and treat or test and scope for Helicobacter pylori infection. Any change in gastric cancer prevention?

A 'test and treat' strategy is advocated for patients with dyspepsia under the age of 45 years, with endoscopy reserved for those with alarm symptoms or aged over 45 years. One of the consequences of this strategy will be a reduction in population infection rates of Helicobacter pylori. It is now clear that H. pylori is one of the prime initiators of gastric cancer with up to 70% of gastric cancers attributable to H. pylori. What remains unclear is if H. pylori reduction will lead to a reduction in gastric cancer.

Gastric cancer epidemiology and risk factors

We performed a detailed analysis of the epidemiology of gastric carcinoma, based upon a review of the literature in English. The analysis reveals many puzzling features. There has been a steady fall in the incidence of gastric carcinoma in most societies studied, but a more recent steady rise in the incidence of adenocarcinoma of the cardia and lower esophagus, largely confined to White males. Although the evidence for a major role for Helicobacter pylori (H. pylori) in the etiology of gastric corpus cancer is compelling; in Western society, it probably accounts for fewer than half the cases. The relative roles of dietary constituents such as salt and nitrites and the phenotyping of H. pylori in causation and the beneficial effects of a high fruit and vegetable diet and an affluent lifestyle, for all of which there is some evidence, are yet to be quantified.

A rational approach to uninvestigated dyspepsia in primary care: review of the literature

In this paper the rationale and limitations of the four most important approach strategies to dyspepsia in primary care (empiric treatment, prompt endoscopy, "test-and-scope", and "test-and-treat") are analysed. It is concluded that in the absence of alarm symptoms, a "test-and-treat" approach is currently the most rational approach provided that three conditions are met: (1) a highly accurate test should be used, (2) the prevalence of Helicobacter pylori in the population should not be too low, and (3) an effective anti-H pylori regimen should be prescribed taking sufficient time to instruct and motivate the patient.

Helicobacter pylori infection on the risk of stomach cancer and chronic atrophic gastritis

Helicobacter pylori infection is associated with gastric adenocarcinoma. However, the mechanisms of this interaction are still unclear. This study was conducted to explore the effects of H. pylori infection on early and late stage gastric carcinogenesis. This study included 134 patients with adenocarcinoma of the stomach (ACS), 67 patients with chronic atrophic gastritis (CAG), and 65 normal controls recruited at Memorial Sloan-Kettering Cancer Center (MSKCC) from November 1, 1992 to November 1, 1994. Epidemiologic data were collected by a modified National Cancer Institute Health Habits History Questionnaire. H. pylori infection was diagnosed by pathological evaluation. Risk factors were analyzed using logistic regression. The odds ratio (OR) associated with H. pylori infection was 10.4 [95% confidence interval (CI): 2.6-41.6] for CAG and 11.2 (95% CI: 2.5-50.3) for gastric cancer in comparison with normal controls, with adjustment for pack-years of smoking, alcohol drinking, body mass index, total caloric intake, dietary fat and fiber intake, and Barrett's esophagus. But H. pylori infection was not associated with risk of stomach cancer when patients with stomach cancer were compared with patients with CAG (OR = 0.6, 95% CI: 0.3-1.3) after controlling for potential confounding variables. This association was persistent when only patients with both gastric cancer and chronic gastritis were considered as cases and patients with CAG were considered as controls (OR = 0.7, 95% CI: 0.3-2.0) in the multivariate analysis. Our results suggest that H. pylori infection may be involved in the early stage of development of CAG, but not in the development of stomach cancer from CAG, and indicate that strategies for prevention of stomach cancer should target the early stage to eliminate H. pylori infection in high-risk populations.

Association of Helicobacter pylori infection with gastric carcinoma: a meta-analysis

OBJECTIVE

As conflicting studies have recently been published, we aimed to determine if Helicobacter pylori (H. pylori) infection is associated with gastric adenocarcinoma.

METHODS

This was a meta-analysis of observational epidemiological studies.

RESULTS

A total of 42 studies met the selection criteria and were categorized by the type of study design: eight cohort and 34 case-control studies. The pooled odds ratio for H. pylori in relation to gastric carcinoma was 2.04 (95% CI: 1.69-2.45). Both patient age (OR 0.77, 95% CI: 0.68-0.89) and intestinal type cancers (OR 1.14, 95% CI: 1.05-1.25) were independent effect modifiers. Analysis of other effect modifiers showed no relationship with female gender (OR 0.76, 95% CI: 0.64-0.89), stage of cancer (advanced %) (OR 1.12, 95% CI: 0.88-1.43), anatomical location (cardia %) (OR 1.54, 95% CI: 0.32-7.39) or cohort (nested case-control) studies (OR 1.72, 95% CI: 0.32-9.17). There was significant heterogeneity among the studies (tau2 = 149; p < 0.001). The quality of the studies varied considerably, with the majority of excellent studies producing positive results and the very poor to moderate studies producing mixed results.

CONCLUSIONS

H. pylori infection is associated with a 2-fold increased risk of developing gastric adenocarcinoma.

Helicobacter pylori infection and gastric cancer: systematic review of the epidemiological studies

BACKGROUND

The published epidemiological studies of chronic Helicobacter pylori infection and gastric cancer yield conflicting results, so there is uncertainty as to whether any material association exists and, if so, how strong it is.

AIM

To review these studies quantitatively.

METHODS

A systematic review of sero-epidemiological studies published before 1998 of H. pylori and gastric cancer, as identified by computer-assisted literature searches of relevant journals, reference lists and discussions with authors. All relevant studies identified were included, subdivided by study design. The following was abstracted from published reports: adjusted odds ratio (or, in prospective studies, the risk ratio) and confidence interval, study design, type of controls, mean age, mean duration of follow-up, assay methods, location of study, and degree of adjustment for confounders.

RESULTS

The 34 retrospective studies included in total 3300 gastric cancers, but their controls were of uncertain validity. The 10 'nested' case-control comparisons in prospective studies included in total only 800 gastric cancers, and combined analysis of them yielded a risk ratio of 2.5 (95% CI: 1.9-3.4; 2P < 0.00001) for gastric cancer in people seropositive for H. pylori antibodies.

CONCLUSIONS

The prospective studies suggest that gastric cancer is 2 or 3 times as common in those chronically infected by H. pylori, but to help investigate causality, further observational studies are still needed, as are large-scale randomized trials of whether antibacterial regimens reduce the eventual incidence of gastric cancer.

Differential Helicobacter pylori infection rates in two contrasting gastric cancer risk regions of South China. China Gastric Cancer Study Group

BACKGROUND

Carriers of Helicobacter pylori are believed to have a three- to six-fold increased risk of developing gastric cancer. We have recently conducted a simultaneous cross-sectional population study on the prevalence of H. pylori infection in a cohort of asymptomatic adult volunteers in two contrasting gastric cancer risk regions of South China, Hong Kong and Changle of Fujian. Their mean annual gastric cancer mortality has been approximately 7.5 and 75/100 000 population, respectively, since the beginning of the last decade. The aim of this study was to evaluate if H. pylori prevalence bears any relationship to gastric cancer mortality rates in these two southern regions of China.

METHODS

Sera were obtained from 397 volunteers in Hong Kong. They were tested for anti-H.pylori immunoglobulin (Ig) G antibody by using a commercial enzyme-linked immunosorbent assay (ELISA) kit. Volunteers of Changle (1456) had upper endoscopy examination and were also tested for anti-H. pylori IgG antibody by the same ELISA method.

RESULTS

The overall H. pylori infection prevalence was significantly higher in Changle (80.4%) than in Hong Kong (58.4%; P< 0.01). The high prevalence is associated with more atrophic gastritis. The overall risk of gastric cancer in people of Changle is approximately five-fold that of Hong Kong (adjusted odds ratio 4.9, 95% CI 2.5-9.8).

CONCLUSIONS

It is concluded that the prevalence of H. pylori infection rates bear a direct relationship to gastric cancer mortality rates in these two southern regions of China. Thus, H. pylori most likely plays a significant aetiopathogenetic role in gastric carcinogenesis in subjects living in Changle.

Epidemiology of gastric cancer in relation to diet and Helicobacter pylori infection

Gastric cancer is the second most common fatal malignancy in the world. In China, gastric cancer is now the second most common malignancy, while in Hong Kong, the mortality rate ranked fourth among all cancers in 1995. Dietary factors in gastric carcinogenesis came mostly from case-control studies. N-Nitroso compounds from dietary sources such as preserved, smoked and salted foods were found to be associated with gastric cancer. ß-Carotene, selenium and α-tocopherol have been shown in an intervention study to be favourable in the reduction of stomach cancer mortality. Fruits and vegetables showed the most consistent results of inverse association with gastric cancer. Dietary salt intake in preserved or salted foods is also shown to be associated with gastric cancer. Tea drinking, especially green tea, has a protective effect against gastric cancer as shown in some studies. Prospective case-control studies of the association between Helicobacter pylori infection and the subsequent development of gastric cancer showed that the odds ratio ranged from 2.8 to 6.0. However, results of similar case-control studies in countries with a high frequency of gastric cancer are controversial. Infection with H. pylori leads to changes in the vitamin C content of gastric juice, reactive oxygen metabolites, epithelial cell proliferation and apoptosis. Recently, CagA-positive strains were found to be associated with gastric cancer and also duodenal ulcers. The exact role of H. pylori in gastric carcinogenesis is still under investigation. Large-scale intervention studies are underway to examine dietary supplementation, H. pylori infection and gastric cancer. Helicobacter pylori eradication for gastric cancer prevention is being conducted in China and other parts of the world. In high-risk areas, for example in China, a combination approach including H. pylori eradication and dietary supplementation may be necessary.

Helicobacter pylori infection and gastric neoplasia: correlations with histological gastritis and tumor histology

OBJECTIVE

Several authors have reported an association between Helicobacter pylori (H. pylori) and gastric carcinoma, but the data are conflicting. Atrophic gastritis and intestinal metaplasia (IM) have also been linked to gastric carcinoma, especially the intestinal tumor type. We investigated the relationship between H. pylori infection, gastric neoplasms, and histological gastritis.

METHODS

A total of 105 patients with gastric carcinoma, 36 patients with gastric adenoma, and 105 age- and sex-matched control subjects were examined for H. pylori infection and histological gastritis. H. pylori status was evaluated by Giemsa staining and IgG serology. Mucosal inflammation, atrophy, and IM were evaluated in biopsy specimens from antrum and corpus.

RESULTS

H. pylori seroprevalence was higher in patients with gastric carcinoma (98 of 105, 93%) and adenoma (34 of 36, 94%) than in control subjects (82 of 105, 71%, p < 0.05). H. pylori was more prevalent in patients with noncardia (OR, 5.67; 95% CI, 2.25-14.44) than cardia (OR, 5.20; 95% CI, 0.65-41.68) tumors. Histologic types and tumor stage (early; OR, 6.60; 95% CI, 2.23-19.69, advanced; OR, 4.27; 95% CI, 1.21-15.03) showed no difference in H. pylori prevalence. Atrophy and IM scores were higher in patients with the intestinal- but not diffuse-type of carcinoma and adenoma than in H. pylori-positive control subjects. Smoking was associated with gastric carcinoma (OR, 3.05; 95% CI, 1.58-5.93) but not alcohol or coffee use, blood group A, or a family history of gastric cancer.

CONCLUSIONS

Our results confirm a strong association between H. pylori and gastric carcinoma and adenoma. The intestinal-type gastric carcinoma is associated with atrophic gastritis and IM.

Meta-analysis of the relationship between Helicobacter pylori seropositivity and gastric cancer

BACKGROUND & AIMS

Reports in the literature regarding the relationship of Helicobacter pylori infection to gastric cancer are conflicting. The aim of this study was to identify the source of heterogeneity between studies.

METHODS

Meta-analysis of cohort or case-control studies with age- and/or sex-matched controls, providing raw data on H. pylori infection detected by serology, was used.

RESULTS

A fully recursive literature search identified 19 qualified studies with 2491 patients and 3959 controls. Test for homogeneity found a significant difference in odds ratio between patients with early and advanced gastric cancer (6.35 vs. 2.13; P = 0.01), patients with cardiac and noncardiac gastric cancer (1.23 vs. 3.08; P = 0.003), and population- and hospital-based controls (2.11 vs. 1.49; P < 0.001). The summary odds ratio for gastric cancer in H. pylori-infected patients is 1.92 (95% confidence interval [CI], 1.32-2.78), 2.24 (95% CI, 1.15-4.4), and 1.81 (95% CI, 1.16-2.84) for all studies, cohort, and case-control studies, respectively. H. pylori-infected younger patients have a higher relative risk for gastric cancer than older patients with odds ratios decreasing from 9.29 at age < or = 29 years to 1.05 at age > or = 70 years. H. pylori infection is equally associated with the intestinal or diffuse type of gastric cancer.

CONCLUSIONS

H. pylori infection is a risk factor for gastric cancer. The heterogeneity of reported results is caused by differences in the selection of controls, patient age, and the site and stage of gastric cancer.

Association between Helicobacter pylori and gastric carcinoma in the city of Malmö, Sweden. A prospective study

BACKGROUND

We have investigated the association between Helicobacter pylori and gastric carcinoma through a nested case-control study in a single city.

METHODS

From a cohort of 32,906 residents recruited from 1974 through 1992, 56 cases of gastric adenocarcinoma and 224 matched controls were selected. The mean interval between serum collection and diagnosis was 5.7 years. Frozen serum or plasma samples were analysed for IgG antibodies against H. pylori with an enzyme-linked immunosorbent assay.

RESULTS

The overall seropositivity prevalence in gastric cancer cases was 82%, compared with 49% in controls, giving an odds ratio (OR) of 5.0 (95% confidence interval (CI), 2.2-11.5). Partial gastrectomy because of peptic ulcer 5 to 36 year before diagnosis of gastric cancer could be a confounding factor. With exclusion of 10 such cases, H. pylori seropositivity among cases was 78%, as compared with 50% in matched controls (OR, 3.9; 95% CI, 1.7-9.2). Tumours of the cardia were not associated with H. pylori (OR, 0.92; 95% CI, 0.23-3.7), which is in contrast to tumours of the fundus, corpus, and antrum, which were significantly associated (OR, 11.1; 95% CI, 2.4-71.8). This difference in location was significant (P < 0.01).

CONCLUSION

There is a significant association between prior infection with H. pylori and later development of gastric carcinoma, and the association is related to noncardia gastric cancer.

Diagnostic accuracy of a rapid whole-blood test for detection of Helicobacter pylori

In this study, we evaluated a rapid whole-blood test, BM-test Helicobacter pylori, for detection of H. pylori infection in 144 and 48 patients with other gastrointestinal symptoms and with gastric cancer, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the test correlated well with the standards used for the calculation, i.e., serology by enzyme-linked immunosorbent assay or culture and histology.

Gastric cancer and Helicobacter pylori: a critical evaluation of the epidemiological evidence

Despite a dramatic reduction in incidence and mortality, gastric cancer (GC) still was recently reported to be the second most common neoplastic cause of death worldwide. GC treatment has not been improved substantially, and large-scale early diagnosis programs have not proved feasible outside Japan. On the other hand, even if diet has been shown to play a relevant role in the etiology of GC, primary prevention programs based on dietary modifications are difficult to implement, and results of human chemoprevention trials, although encouraging, have not been confirmed. Overall, the observed reduction in GC risk can reasonably be considered to be the result of a spontaneous trend, somehow related to the wide-spread improvements in socioeconomic conditions. Domestic refrigeration, an increased availability of fresh fruit and vegetables, and a reduced use of salt are considered to be the most relevant factors in explaining the decreasing temporal trend and the geographical patterns of GC. Recently, evidence of an association between Helicobacter pylori infection and GC has been provided by epidemiological studies, particularly three studies specifically designed as nested case-control studies in which blood samples were collected well before diagnosis was made. The results of these studies, however, have been confirmed only in part. A strong direct association is not yet widely accepted, and no specific carcinogenic compound or mechanism has been identified. Relevant aspects of GC and H. pylori epidemiology actually do not fit perfectly in a causal hypothesis (i.e., the geographical and gender distribution, the paradoxical association with duodenal ulcer) though, on the other hand, several other factors certainly play a role in the complex multifactorial process leading, over several decades, to GC. Studies focused on H. pylori eradication and its effects on lesions that predispose to GC (atrophic gastritis and metaplasia), however, represent a priority for research, in view of the potential preventive applications. This issue remains controversial, and it is possible that progression of these lesions might occur after eradication.

Relation between histologic subtypes and location of gastric cancer and Helicobacter pylori

BACKGROUND

Epidemiologic studies have consistently shown an association between Helicobacter pylori infection and gastric cancer, and it is now widely accepted that this organism plays a role in the pathogenesis of this tumor. Nevertheless, there are discrepant results on its relationship with the histologic type and location of gastric cancer within the stomach. The aim of this study was to determine the seroprevalence of H. pylori in a group of gastric cancer patients and the association between H. pylori and specific histologic types of gastric cancer and tumor location within the stomach.

METHODS

Systemic IgG antibodies against H. pylori were assayed using an enzyme-linked immunosorbent assay technique in 48 patients (male to female ratio, 31:17; age range, 39-88 years; mean, 69 years) with histologically confirmed gastric cancer and 50 controls (male to female ratio, 33:17; age range, 40-77 years, mean, 64 years).

RESULTS

Thirty-one cases of gastric cancer were of the intestinal type, and 12 of the diffuse type; the remaining 5 were unclassified. Thirteen gastric cancers were located in the distal stomach (antrum/pylorus), 12 in the body, and 5 in the proximal stomach (cardia/fundus); the remaining 17 were unclassified because the tumor extended towards more than one location. The overall seroprevalence of H. pylori in patients with gastric cancer and controls was 85.4% and 66%, respectively (P < 0.05). The seroprevalence increased with increasing age in cancer patients, but the difference was not significant. H. pylori seroprevalence among patients with the intestinal type of gastric cancer was higher than in those with the diffuse type (P < 0.05). The prevalence of H. pylori infection was higher among patients with the cancer located distally than in those with the cancer located proximally (P < 0.05).

CONCLUSIONS

H. pylori seroprevalence was higher in gastric cancer patients than in controls. The prevalence of H. pylori infection in intestinal-type gastric cancer was clearly higher than in the diffuse type and in the control group. An association was found between H. pylori infection and tumors located distally (antrum/pylorus).

The proliferation of human T lymphocytes stimulated by Helicobacter pylori antigens

Fractionated mononuclear cells (MNCs) were obtained from peripheral blood of healthy human volunteers, seronegative for H. pylori antibodies. The MNCs were stimulated in culture with whole live or heat-killed H. pylori cells or with bacterial cell surface (SA) or cytoplasmic (CA) antigens. There was a marked proliferative response of T cells in cultures stimulated with 10(5) cells/well of live H. pylori, 5 micrograms/well of CA or 5-20 micrograms/well of SA. However, no proliferation was observed in MNC cultures containing higher "doses" of live H. pylori organisms (10(7)/well) or CA (20 micrograms/well). Moreover, higher "doses" of the bacteria or CA entirely inhibited the response of T cells to PHA.

Helicobacter pylori and gastric carcinogenesis

BACKGROUND

Helicobacter pylori causes chronic persistent gastritis in virtually all infected subjects, leading to development of atrophic gastritis, intestinal metaplasia and eventually dysplasia and gastric cancer in a number of infected subjects. Based on the available evidence, an IARC monograph committee classified H. pylori as a class I carcinogen to humans. Prospective studies suggest that infection increases the risk for atrophic gastritis and gastric cancer at least 8-fold. In the presence of infection, the risk for atrophy and cancer seems higher if a subject becomes infected in early childhood, if infection occurs with a cagA positive strain, and if acid output is decreased.

CONCLUSION

H.pylori is a gastric carcinogen. The clinical implications and possible strategies for cancer prevention have to be delineated in the near future.

Simultaneous gastric adenocarcinoma and MALT-type lymphoma in Helicobacter pylori infection

A 79-year-old women with upper abdominal pain, vomiting and weight loss was found at endoscopy to have a large tumour mass in the gastric body. Histology of forceps biopsies revealed an adenocarcinoma of intestinal type. Gastrectomy was performed, but extensive lymph node metastasis precluded a curative surgical approach. Histopathological study of the specimen, however, revealed two distict malignancies, which arose in the setting of Helicobacter pylori-associated chronic gastritis with partial mucosal atrophy. One tumour was a gastric carcinoma, while the other was a primary B-cell lymphoma of the stomach (CD20-positive). The lymphoma comprised both a low-grade component (mucosa-associated lymphoid tissue- or MALT-type lymphoma), and a high-grade component (large cell lymphoma with CD30-positive giant cells). Infection with H. pylori was confirmed by the serological presence of IgG antibodies to H. pylori-antigens, including antibodies against the 128 kDa protein of the cytotoxin-associated gene (cagA gene) of H. pylori.

Lack of association of Helicobacter pylori seroprevalence and gastric cancer in a population with low gastric cancer incidence

BACKGROUND

Previous studies have suggested that infection with Helicobacter pylori is associated with an increased risk of gastric adenocarcinoma.

METHODS

We examined the sera of 111 Caucasian patients with histologically confirmed gastric cancer (36 with cancer of the cardia, 70 with cancer of the body or antrum, and 5 with stump carcinomas after Billroth-II procedures) and 111 age-matched controls with colorectal carcinomas for the presence of H. pylori IgG antibodies by enzyme-linked immunoassay.

RESULTS

The overall prevalence of H. pylori infection was 58.6% (65 of 111) in gastric cancer patients as compared with 50.5% (56 of 111) in matched control subjects (odds ratio, 1.39; 95% confidence interval, 0.82 to 2.36). Carcinomas of the cardia were not linked to H. pylori infection (odds ratio, 1.25; 95% confidence interval, 0.65 to 2.46), nor diffuse or intestinal-type carcinomas (odds ratios, 1.79 and 1.0; 95% confidence intervals, 0.69 to 4.67 and 0.34 to 2.91, respectively). Age, sex, and height of the IgG immune response did not affect risk.

CONCLUSIONS

In contrast to previous results, these data do not provide evidence that the contribution of H. pylori infection to the carcinogenesis of gastric cancer is of major significance in a population with low gastric cancer rates and with high socioeconomic status.

Helicobacter pylori as a risk factor for cancer

In 1985, gastric cancer was the second most common cause of cancer death in the world. The rapid decline in gastric cancer rates over the last few decades has been attributed to a decline in the prevalence of environmental risk factors for gastric cancer and/or an increase in the prevalence of protective factors. One such risk factor could be the bacterium Helicobacter pylori. Epidemiological studies have shown that areas with high gastric cancer rates often have a correspondingly high prevalence of H. pylori and prospective studies have shown that subjects with serological evidence of H. pylori infection were significantly more likely to go on to develop gastric cancer than those who did not. Helicobacter pylori itself does not appear to be either genotoxic or mutagenic. Infection is, however, associated with increased cell turnover, a chronic immune response accompanied by increased levels of reactive oxygen metabolites and a reduction in gastric levels of ascorbic acid, all conditions that could favour the development of cancer. Nonetheless, the majority of those who are infected with H. pylori do not go on to develop gastric cancer and other factors, such as the strain of the infecting organism or consumption of dietary antioxidants including vitamin C, could also affect the risk of cancer. Finally, it has been estimated that more than one third, and possibly as many as 90% of gastric cancers might be attributable to infection with H. pylori. Prevention and treatment of infection are, therefore, possible approaches to reducing gastric cancer rates. It is, however, unclear what, if any, effect eradication of the infection would have on an individual's risk of gastric cancer and, to date, anti-Helicobacter therapy has only been shown to be of potential benefit in the treatment of low grade gastric MALT lymphomas.

Is Helicobacter pylori infection a real risk factor for gastric carcinoma?

BACKGROUND AND METHODS

That Helicobacter pylori has a role in the pathogenesis of gastric carcinoma is widely accepted, although not all doubts are definitively clarified. The purpose of this work was to detect the differences in presence and mean titer of anti-H. pylori antibodies between groups with gastric (n = 65), colonic (n = 70), and lung (n = 43) carcinoma.

RESULTS

The highest prevalence of anti-H. pylori antibodies was found in patients with pulmonary carcinoma (88.4%), which significantly surpassed (p = 0.02) that in the group with gastric carcinoma (69.2%). The groups with colonic and gastric carcinomas failed to show any difference in this respect. Mean antibody titer was significantly higher in subjects with lung carcinoma than in those with gastric carcinoma (p = 0.005). This difference was unrelated to age.

CONCLUSIONS

These results contradict the hypothesis assuming a relationship between H. pylori infection and the sequence of phenomena leading to gastric carcinoma.

Diagnosis of gastric adenocarcinoma using a scoring system: combined assay of serological markers of Helicobacter pylori infection, pepsinogen I and gastrin

This study was carried out to develop a scoring system for the diagnosis of gastric adenocarcinoma (GAC). A total of 686 subjects, 150 patients with GAC, 182 with gastric ulcer, 127 with duodenal ulcer, and 227 subjects with negative findings, were enrolled. Analysis of the likelihood ratio (LR) showed that patients with advanced age, ulcer in the stomach, low serum levels of pepsinogen I (PGI), low PGI x gastrin values, and low PGI/gastrin ratio were likely to have GAC. Of these indicators, the serum PGI level had the greatest weight, with a LR of 7.59 for the group with a level < 30 ng/ml. A scoring system combining serum PGI level, Helicobacter pylori seropositivity, and gastric ulcer status was derived, using a logistic regression model. This scoring system was found to be better than any one-parameter criterion for diagnosing GAC after evaluation by the area under the receiver operating characteristic curve (0.84; 95% confidence interval, 0.81-0.88) or by specificity-fixed sensitivity (sensitivity 0.82 at specificity 0.72, sensitivity 0.87 at specificity 0.66, sensitivity 0.96 at specificity 0.44). This scoring system may be potentially useful as a new model for the noninvasive diagnosis of GAC in the future.

Bacteria in the aetio-pathogenesis of gastric cancer: a review

Severe atrophic gastritis, a precursor lesion of gastric carcinoma, is connected, in two different ways, with intragastric bacterial colonization: (1) in advanced atrophic body gastritis (type A), achlorhydria or severe hypochlorhydria leads to bacterial overgrowth with aerobic and anaerobic flora enabling the conversion of nitrate to nitrite and further to N-nitroso compounds; (2) the newly re-discovered Helicobacter pylori is probably one of the major causes of chronic atrophic antral gastritis (type B). Both types of bacteria may be involved in the pathogenesis of multifocal gastritis (type AB). In the western world, achlorhydric atrophic gastritis is not only found in pernicious anaemia but is latent in about 2 to 6% of the general population. In one study from the Mayo Clinic, about one-third of consecutive gastric carcinomas were present in achlorhydric stomachs, the remainder in acid-secretors. Apart from the N-nitroso compounds, other carcinogenic mechanisms may be active in type A gastritis: elevated serum gastrin; altered cell turnover; immunologic and hereditary traits. The association of H. pylori with gastric carcinoma is mainly based on circumstantial evidence: (i) epidemiological studies indicate a moderately increased risk for gastric cancer in H. pylori-positive subjects compared with H. pylori-negative; (ii) in the presence of H. pylori intragastric levels of the anti-oxidant ascorbic acid are lowered; (iii) H. pylori seems to be linked to mucosal atrophy and intestinal metaplasia; (iv) recent follow-up studies show a significant development of atrophic gastritis in H. pylori-positive patients compared to H. pylori-negative.(ABSTRACT TRUNCATED AT 250 WORDS)

Seroconversion for Helicobacter pylori

The prevalence of Helicobacter pylori antibodies increases with age, but it is unknown whether this is due to a constant rate of infection in different age groups, or whether most infection occurs in childhood. Follow-up data on infection rates and the course of infection in an untreated population are scarce. We measured H pylori IgG antibody concentrations in patients who were seen at our endoscopy unit between 1979 and 1983. 115 of 164 eligible patients (70%) participated in the study. H pylori IgG antibody concentrations were measured in two serum samples taken with a mean interval of 11.5 years. 56 patients tested positive at the first visit. During follow-up, 2 patients became infected (annual infection rate 0.30%, 95% Cl 0.04-1.08%). Evidence of infection disappeared in 6 patients: after gastric surgery in 3 and due to an unknown cause in the remaining 3 patients. A non-significant decrease of infection was shown in different age cohorts during follow-up. Antibody concentrations did not increase with age. These results strongly support the concept of dominant infection rates in childhood. Elimination of infection may occur in a few patients without eradication therapy.