Treatment of Helicobacter pylori and prevention of gastric cancer

Gastric cancer is the second commonest fatal malignancy in the world with a high incidence in China. Helicobacter pylori infection is an important factor in the pathogenesis of gastric cancer. Epidemiological studies have shown a strong causal relationship between H. pylori infection and gastric cancer. Animal studies also show that eradication of H. pylori infection, especially at the early stage, is effective in preventing H. pylori-related gastric carcinogenesis. H. pylori eradication leads to regression and prevents the progression of gastric precancerous lesions, but only in a minority of cases. H. pylori eradication appears to be the most promising approach in gastric cancer prevention. The current available data in human studies showed that H. pylori eradication can reduce the risk of developing gastric cancer and this strategy is more useful in patients without atrophic gastritis or intestinal metaplasia. A longer follow-up and additional studies are needed for better understanding this issue.     

Eradication of H pylori for the prevention of gastric cancer

Infection with H pylori is the most important known etiological factor associated with gastric cancer. While colonization of the gastric mucosa with H pylori results in active and chronic gastritis in virtually all individuals infected, the likelihood of developing gastric cancer depends on environmental, bacterial virulence and host specific factors. The majority of all gastric cancer cases are attributable to H pylori infection and therefore theoretically preventable. There is evidence from animal models that eradication of H pylori at an early time point can prevent gastric cancer development. However, randomized clinical trials exploring the prophylactic effect of H pylori eradication on the incidence of gastric cancer in humans remain sparse and have yielded conflicting results. Better markers for the identification of patients at risk for H pylori induced gastric malignancy are needed to allow the development of a more efficient public eradication strategy. Meanwhile, screening and treatment of H pylori in first-degree relatives of gastric cancer patients as well as certain high-risk populations might be beneficial.     

Causal role of Helicobacter pylori infection in gastric cancer

Gastric cancer is the second most frequent cancer in the world, accounting for a large proportion of all cancer cases in Asia, Latin America, and some countries in Europe. Helicobacter pylori(H pylori) is regarded as playing a specific role in the development of atrophic gastritis, which represents the most recognized pathway in multistep intestinal-type gastric carcinogenesis. Recent studies suggest that a combination of host genetic factors, bacterial virulence factors, and environmental and lifestyle factors determine the severity of gastric damage and the eventual clinical outcome of H pylori infection. The seminal discovery of H pylori as the leading cause of gastric cancer should lead to effective eradication strategies. Prevention of gastric cancer requires better screening strategies to identify candidates for eradication.     

Prevention of gastric cancer by Helicobacter pylori eradication

The evidence supporting the important role of Helicobacter pylori causing gastric cancer is getting stronger. The mechanisms by which H. pylori can influence the progression to severe changes in the gastric mucosa are under investigation. An increased gastric epithelial cell proliferation has been observed in individuals infected with H. pylori. This lifelong increased cell turnover is deemed to be a major risk factor for increased mutational changes and may lead to the development of gastric cancer. Successful eradication of H. pylori infection induces the healing of the gastritis and a significant decrease in gastric epithelial cell proliferation. Nevertheless, it is right now unknown at which time the point of no return, meaning at which time an eradication therapy leads to a benefit for the individual to prevent gastric cancer, has been reached. Therefore the major question that arises is to whom an eradication therapy should be offered to prevent gastric cancer. A general elimination of the infection might be worthwhile, but seems to be unrealistic now because of the high prevalence of the infection and the missing of a vaccine. This review reflects possible mechanisms of gastric cancer development induced by chronic H. pylori infection and recent investigational trials for prevention of gastric cancer by H. pylori eradication therapy will be discussed.     

Helicobacter pylori infection and development of gastric cancer in Korea: long-term follow-up

BACKGROUND AND AIM: Infection of Helicobacter pylori is viewed as a major driver of progression to the precancerous state or to gastric cancer. This study was performed to investigate the effect of H. pylori infection on gastric cancer development and to determine to what extent H. pylori eradication is likely to reduce the prevalence of gastric cancer. METHODS: Gastric cancer development was investigated in 1790 Korean subjects who underwent gastroscopy and H. pylori testing between 1992 and 1998. The effects of H. pylori-positive and eradicated states on gastric cancer development were analyzed. RESULTS: Gastric cancer developed in 5 of the study cohort during a mean follow-up period of 9.4 years. All of these patients were positive for H. pylori infection, and 4 of the 5 had antral intestinal metaplasia (IM) at the time of study enrollment. One of these 5 patients was in an eradicated state when the gastric cancer was diagnosed, and had histologic IM before eradication therapy was performed. Gastric cancer was found to develop 10.9 times more frequently in the presence of IM than in its absence. CONCLUSIONS: The present study shows a close relationship between H. pylori infection and IM, and between IM and the development of gastric cancer. In addition, our finding suggests that chronic H. pylori infection looks like an important risk factor for the development of gastric cancer in Korea, where the prevalence of H. pylori remains high. This study indicates that to prevent gastric cancer H. pylori eradication is best performed before the development of IM.     

The effect of Helicobacter pylori eradication on reducing the incidence of gastric cancer

Epidemiologically, the association between chronic Helicobacter pylori infection and development of gastric cancer is well established. Although the possibility of preventing gastric cancer by eradicating H. pylori infection was recently investigated by several research groups, the results remain controversial. The aim of this study was to determine whether the eradication of H. pylori infection would reduce the incidence of gastric cancer. In total, 304 patients with persistent H. pylori infection and 404 patients with H. pylori infection eradicated were examined annually for gastric cancer by endoscopy. Over an average of 3.1 years for the first group and 3.2 years for the second group, 13 and 6 patients, respectively, were diagnosed as having new gastric cancer. The cumulative incidence of gastric cancer was statistically different between the groups (P=0.019; log-rank test). The hazard ratio of H. pylori eradication was 0.335 by Cox proportional hazards model (P=0.047). Differentiated gastric cancer was found in 11 patients in the persistent infection group and 3 patients in the eradicated group. The incidence of differentiated cancer was significantly different (P=0.017) between the groups, but not for undifferentiated cancer (P=0.847). The results of the current study suggest that the eradication of H. pylori infection reduces the incidence of gastric cancer.     

Clinical prevention of gastric cancer by Helicobacter pylori eradication therapy: a systematic review

Helicobacter pylori (H. pylori) infection plays an important role in gastric carcinogenesis. We conducted a systematic review concerning gastric cancer development after H. pylori eradication therapy. In total 15 papers matched our criteria, the results were reviewed. The H. pylori eradication therapy statistically diminished the prevalence of clinical gastric cancer by approximately one-third. The studies from Japan supported this conclusion; however, studies from overseas reported conflicting results. The differences in these conclusions lie in the diagnostic ability of endoscopic examination, since the clinical stage was quite different between these studies. Gastric cancer that developed after eradication revealed a mainly intestinal type histology and depressed-type appearance. The following are possible reasons for reduced gastric cancer: (1) eradication therapy inhibits the new occurrence of gastric cancer, (2) eradication regresses or inhibits the growth of gastric cancer, and (3) eradication interferes with the discovery of gastric cancer. Considering the biological nature of cancer cell proliferation, a sufficiently long-term follow-up may clarify the effect of eradication therapy on inhibition of the development (not discovery) of gastric cancer and reduction of gastric cancer-related mortality.     

Characteristics and predictors of gastric cancer after Helicobacter pylori eradication

Helicobacter pylori(H. pylori) eradication can reduce gastric cancer. However, gastric cancer still develops after eradication, and cases who received eradication therapy are increasing. In this study, we have reviewed the characteristics and predictors of primary gastric cancer developing after H. pylori eradication. In terms of the characteristics, endoscopic, histologic, and molecular characteristics are reported. Endoscopically, gastric cancer after eradication is often depressedtype and shows a gastritis-like appearance, which sometimes makes the diagnosis difficult. Histologically, most gastric cancer after eradication is intestinal type, and non-neoplastic epithelium, also called epithelium with low-grade atypia, is frequently seen over the tumor, which is presumably the cause of the endoscopic gastritis-like appearance. As for molecular characteristics, some markers, such as Ki67, MUC2, and Wnt5a expression, are lower in cancer from patients in whom H. pylori has been eradicated. In terms of predictors, several Japanese studies have reported that severe endoscopic atrophy at eradication is a risk factor for gastric cancer development. Histologic intestinal metaplasia, especially in the corpus, and long-term use of proton pump inhibitors, are also reported as risk factors for gastric cancer after H. pylori eradication. These studies on the characteristics and predictors of gastric cancer development will become the cornerstone for establishing a novel surveillance program based on the gastric cancer risk stratification specific to H. pylori-eradicated patients.     

Helicobacter pylori infection and gastric cancer

According to several prospective controlled epidemiologic studies, the positive rate of H. pylori antibody was shown to be higher in the patients with gastric cancer than in the control group. Retrospective studies on the association between gastric cancer and H. pylori have been conducted in a large number of subjects and the results can be classified broadly into two categories, i.e., findings affirming an association and others denying it. Research concerning the association between gastric cancer and H. pylori has achieved great progress over time, leading to the recognition of this relationship by the WHO. One of the greatest concerns is to ascertain whether the final outcome of H. pylori-induced gastritis may lead to gastric cancer. The onset of gastric cancer can be explained as being caused not only by H. pylori infection, but also by a combination of various factors such as food and the environment. However, the possibility that the occurrence of gastric cancer, like the recurrence of peptic ulcer, can be prevented by eradication of H. pylori has also been suggested. Further progress in clinical research is needed to resolve this issue.     

The effect of eradicating helicobacter pylori on the development of gastric cancer in patients with peptic ulcer disease

OBJECTIVES: Infection with Helicobacter pylori is a risk factor for the development of gastric cancer. However, it is not known whether eradication therapy can prevent the development of gastric cancer in persons in whom the cancer is not yet established. In the present study, we investigated whether the eradication of H. pylori in patients with peptic ulcer disease reduces the likelihood of their developing gastric cancer. METHODS: Prospective posteradication evaluations were conducted in 1,342 consecutive patients (1,191 men and 151 women; mean age: 50 yr) with peptic ulcer diseases who had received H. pylori eradication therapy. After confirmation of eradication, endoscopy and a urea breath test were performed yearly. RESULTS: A total of 1,120 patients completed more than 1-yr follow-up and were followed for up to 8.6 yr (a mean of 3.4 yr). Gastric cancer developed in 8 of 944 patients cured of infection and 4 of 176 who had persistent infection (p= 0.04; log-rank test). All the gastric cancer developed in patients with gastric ulcer, but none in patients with duodenal ulcer (p= 0.005; Fisher's exact test). In patients with gastric ulcer, persistent infection was identified as a significant factor for the risk of developing gastric cancer (hazard ratio: 3.35; 95% confidence interval: 1.00-11.22; p= 0.04; Cox's proportional-hazards model). CONCLUSION: H. pylori eradication may reduce their risk of developing gastric cancer in patients with gastric ulcer. Large-scale studies in additional populations of this important international public-health issue are warranted.     

根除幽门螺杆菌在预防胃癌中的作用

胃癌在全球恶性肿瘤致死亡的原因中位居第二位,幽门螺杆菌（H．pylori）感染是胃癌发生的重要病因。动物研究显示根除H.pylori,特别是在早期阶段,能有效预防胃癌的发生。部分病例通过根除npylori可阻止胃癌前病变的发展并可能使其逆转。最新研究表明根除H．pylori可降低胃癌发生的风险,对无萎缩或肠化生者可能尤其有效。本文就根除H．p）tori在预防胃癌中作用的研究进展作一综述。     

From gastric inflammation to gastric cancer

The majority of gastric adenocarcinomas are related to chronic inflammation induced by Helicobacter pylori infection. For intestinal-type gastric cancer, a multistep process of mucosal alterations leading from gastritis via glandular atrophy, intestinal metaplasia and dysplasia to invasive carcinoma is well recognized. Ongoing clinical studies focus on a 'point of no return'. It is defined as a situation when certain alterations are no longer reversible by H. pylori eradication and progression to gastric cancer may continue. H. pylori affects the mucosal as well as the systemic immune response by secretion of cytokines and the recruitment of distinct inflammatory cells. The immune response is characterized by a balance between a Th1-dominated response and the recruitment of antigen-specific regulatory T cells that allow the bacteria to persist in human gastric mucosa. Besides immune-mediated effects, H. pylori induces cellular alterations as well as genetic alterations in genes that are essential for the epigenetic integrity and mucosal homeostasis. These genetic alterations during gastric cancer development are in focus of intensive research and should ultimately allow the identification of risk factors involved in gastric carcinogenesis. The detection of individuals at high risk for gastric cancer would help to design appropriate strategies for prevention and surveillance.     

Prevention of gastric cancer: a challenging but feasible task

Despite its declining incidence gastric cancer still ranks as the second most common malignancy of the digestive tract, accounting for 10% of cancer deaths worldwide. At the time of the diagnosis less than 15% of the patients are in the stage of early cancer, the only stage in which a definite cure of gastric cancer is possible. Therefore the challenges are either early detection or even better prevention of gastric cancer. H. pylori has become recognized as the major risk factor for gastric adenocarcinoma. Epidemiological, biological, histomorphologic, molecular-genetic, epidemiological evidence and more recently few clinical trails have shown that H. pylori eradication has the potential to prevent the development of gastric cancer. Currently H. pylori eradication is an indication for the prevention of gastric cancer in patients and groups of individuals with strongly increased risk, but further investigations are still required before an implementation of a general and global policy to eradicate H. pylori for the prevention of gastric cancer can be instituted. At present time, the main challenge remains to find out at what point mucosal abnormalities are no longer reversible and gastric cancer development cannot be prevented despite H. pylori eradication.     

Helicobacter pylori and gastric cancer

Infection with Helicobacter pylori is now recognized as the primary cause of peptic ulcers and their recurrence. Compelling evidence has also been found linking H. pylori infection to gastric cancer, the second most common cancer in the world. Given the high rate of patient morbidity and mortality associated with gastric cancer, any method by which one can reduce the occurrence of the disease or increase its early detection is desirable. The strong correlation with H. pylori infection and the current availability of easily administered tests for the detection of the pathogen argue for screening at least those individuals with a family history of gastric cancer or other risk factors. This article reviews the association between H. pylori and gastric cancer and the pathologic changes that the infection produces in the gastric mucosa, as well as the cost-effectiveness of universal testing and eradication of the infection in H. pylori-positive individuals to reduce gastric cancer.     

Helicobacter pylori and gastric acid secretion

Helicobacter pylori (H. pylori) infection leads to profound changes in gastric physiology. Several clinical and animal studies have been performed to clarify the influence of H. pylori on gastric acid secretion. Published data, however, are not consistent throughout. Infection of the gastric antrum, which can be observed mainly in duodenal ulcer patients, increases gastrin release and consecutively acid output. The net effect of corpus and antrum gastritis, such as in patients with gastric cancer, is to decrease acid secretion. Chronic H. pylori infection may finally promote gastric atrophy with irreversibly diminished acid secretion but in earlier stages of this infection eradication of H. pylori normalizes gastric secretory activity.     

Can gastric cancer be prevented by Helicobacter pylori eradication?

Helicobacter pylori infection always causes chronic gastritis and triggers several gastroduodenal pathologies ranging from peptic ulcer disease to gastric cancer. It is well established that H. pylori eradication decreases the incidence of gastroduodenal ulcer and its recurrence. However, despite being accepted as the critical risk factor for gastric cancer, there is no conclusive evidence that H. pylori eradication decreases the incidence of gastric cancer. Bacterial virulence characteristics, as well as genetic predisposition of the host in conjunction with certain environmental conditions, are the major factors which influence the development of gastric cancer. Preclinical and clinical data suggest that reversibility of precancerous lesions (atrophic gastritis and intestinal metaplasia) is possible in some patients after H. pylori eradication. Since neoplastic lesions do not progress - or even regress in some cases - after H. pylori eradication, eradication therapy should be considered even in patients with precancerous lesions. Nonetheless, progression of atrophic gastritis and intestinal metaplasia into cancer has been also demonstrated in patients after H. pylori eradication, suggesting that there might be a point of no return where genetic changes have already happened and are irreversible despite elimination of the triggering carcinogen (H. pylori). At the present time the clinical decision to treat a patient is based on established risk profiles. A general screen-and-treat policy, although desirable, currently awaits a less complex treatment regimen.     

Helicobacter pylori-infected animal models are extremely suitable for the investigation of gastric carcinogenesis

Although various animal models have been developed to clarify gastric carcinogenesis, apparent mechanism of gastric cancer was not clarified in recent years. Since the recognition of the pathogenicity of Helicobacter pylori (H pylori), several animal models with H pylori infection have been developed to confirm the association between H pylori and gastric cancer. Nonhuman primate and rodent models were suitable for this study. Japanese monkey model revealed atrophic gastritis and p53 mutation after long-term infection of H pylori. Mongolian gerbil model showed the development of gastric carcinoma with H pylori infection alone, as well as with combination of chemical carcinogens, such as N-methyl-N-nitrosourea and N-methyl-N-nitro-N-nitrosoguanidine. The histopathological changes of these animal models after H pylori inoculation are closely similar to those in human beings with H pylori infection. Eradication therapy attenuated the development of gastric cancer in Hpylori-infected Mongolian gerbil. Although several features of animal models differ from those seen in human beings, these experimental models provide a starting point for further studies to clarify the mechanism of gastric carcinogenesis as a result of H pylori infection and assist the planning of eradication therapy to prevent gastric carcinoma.     

Helicobacter pylori-related diseases: dyspepsia, ulcers and gastric cancer

This article summarizes the main conclusions drawn from the presentations on Helicobacter pylori infection at Digestive Disease Week 2011. In developed countries, the prevalence of H. pylori infection has decreased, but seems to have reached a plateau at a fairly high level. Antibiotic resistance is increasing in several countries. H. pylori eradication does not contribute to the development of gastroesophageal reflux disease or worsen its course. The frequency of idiopathic peptic ulcers seems to be increasing. H. pylori eradication eliminates almost all episodes of peptic ulcer rebleeding; nevertheless, the use of non-steroidal anti-inflammatory drugs or H. pylori reinfection can lead to bleeding recurrence. H. pylori-negative patients with peptic ulcer bleeding more frequently have bleeding recurrences and higher mortality. In each particular population, there is a close correlation between the prevalence of H. pylori infection and the incidence of gastric cancer. H. pylori eradication is associated with a higher and faster healing rate of ulcerous lesions caused by endoscopic submucosal dissection. In patients undergoing endoscopic submucosal dissection for early gastric cancer, H. pylori eradication decreases the incidence of metachronous tumors. In a high proportion of cases, H. pylori eradication induces MALT lymphoma regression, and long-term tumoral recurrences are exceptional. Narrow-band imaging allows visualization of the mucous and vascular pattern in H. pylori-infected patients during the endoscopic examination. The electrochemical properties of H. pylori allow these lesions to be rapidly and accurately detected in gastric biopsies. The efficacy of "traditional" triple therapies currently leaves much to be desired. The superiority of "sequential" therapy over the standard triple therapy should be confirmed in distinct environments. The "concomitant" quadruple therapy seems to be as effective as "sequential" therapy, but with the advantage of being simpler. Both the "sequential" and the "concomitant" regimens are relatively effective even when clarithromycin resistance is present. Second-line rescue therapy with levofloxacin for 10 days is effective and is simpler and better tolerated than quadruple therapy. In patients allergic to penicillin, a combination with levofloxacin and clarithromycin is a promising rescue alternative. The new-generation quinolones, such as moxifloxacin and sitafloxacin, could be useful as eradication treatment. After two eradication treatment failures, an empirical third-line rescue therapy may be a valid option in clinical practice. Even after three previous H. pylori eradication failures, an empirical fourth-line rescue treatment with rifabutin may be effective.     

Molecular alterations in gastric cancer: the role of Helicobacter pylori

Helicobacter pylori has been classified as a human carcinogen contributing to the pathogenesis of gastric cancer. Extensive sero-epidemiological studies and recently animal experiments have established a close link between H. pylori infection and the development of gastric cancer. However, the molecular changes induced by H. pylori directly or the concomitant chronic inflammation of the gastric mucosa, and the impact of these changes on the subsequent development of gastric cancer, remain largely unknown. This review will highlight the present knowledge on the molecular pathogenesis of gastric cancer with an emphasis on molecular and genetic alterations which develop due to chronic infection of the gastric mucosa by H. pylori.     

Helicobacter pylori eradication to prevent gastric cancer： underlying molecular and cellular mechanisms

Numerous cellular and molecular events have been described in development of gastric cancer. In this article, we overviewed roles of Helicobacter pylori (H pylori) infection on some of the important events in gastric car-cinogenesis and discussed whether these cellular and molecular events are reversible after cure of the infection. There are several bacterial components affecting gastric epithelial kinetics and promotion of gastric carci-nogenesis. The bacterium also increases risks of genetic instability and mutations due to NO and other reactive oxygen species. Epigenetic silencing of tumor suppressor genes such as RUNX3 may alter the frequency of phe-notype change of gastric glands to those with intestinal metaplasia. Host factors such as increased expression of growth factors, cytokines and COX-2 have been also reported in non-cancerous tissue in H py/ori-positive subjects. It is noteworthy that most of the above phenomena are reversed after the cure of the infection. However, some of them including overexpression of COX-2 continue to exist and may increase risks for carcinogenesis in metaplastic or dysplastic mucosa even after successful H pylori eradication. Thus, H pylori eradication may not completely abolish the risk for gastric carcinogenesis. Efficiency of the cure of the infection in suppressing gastric cancer depends on the timing and the target population, and warrant further investigation.