Analysis of Relationships between Altitude and Distance from Volcano with Stomach Cancer Incidence Using a Geographic Information System

Epidemiologic Study of Gastric Cancer in Iran: A Systematic Review

BACKGROUND

Gastric cancer (GC) is one of the most common cancers in Iran. Knowledge of the epidemiology of the disease is essential in planning for prevention. So this study aimed to investigate the epidemiological aspects of gastric cancer including prevalence, incidence, mortality, and risk factors of Iran.

METHODS

This systematic review study was based on articles published in both English and Persian languages during the years of 1970-2020 in international databases (PubMed, Web of Science, Scopus) and national databases (including SID, Magiran, and IranDoc). Papers related to epidemiological aspects of the disease including mortality, prevalence, incidence, and risk entered the final review.

RESULTS

According to the studies, the minimum and maximum prevalence of gastric cancer in northwestern Iran (Ardabil) is between 0.2 and 100 per 100,000. Also, the death rate per 100,000 people ranged from 10.6 to 15.72 and the ASMR ranged from 4.2 to 32.2%. On the other hand, the incidence of GC was higher in men than in women (74.9 vs 4.6%). The GC risk ratio was 8-times higher in the elderly than in the other age groups (HR=8.0, 2.7-23.5). The incidence of gastric cancer in patients with H. pylori infection was 18-times and that of smokers 2-times higher than other populations. Low level of economic situation and food insecurity increased the odds of GC by 2.42- and 2.57-times, respectively. It should be noted that there was a direct relationship between consumption of processed red meat, dairy products, fruit juice, smoked and salty fish and legumes, strong and hot tea, and consumption of salt and gastric cancer incidence. There was also an inverse relationship between citrus consumption, fresh fruit, garlic, and gastric cancer. In addition, the mRNA genes are the most GC-related genes.

CONCLUSION

Given the high incidence of GC in Iran, changing lifestyle and decreasing consumption of preservatives in food, increasing consumption of fruits and vegetables, and improving the lifestyle can be effective in reducing the incidence of this disease.

Impact of environmental factors on gastric cancer: A review of the scientific evidence, human prevention and adaptation

Globally, gastric cancer (GC) ranks fifth in prevalence and third in fatalities, and shows a distinct geographical distribution in morbidity and mortality. Such a spatial pattern indicates that environmental factors could be an important contributor to GC. We reviewed a total of 135 relevant peer-reviewed articles and other literature published 1936-2019 to investigate the scientific evidence concerning the effects of environmental factors on GC worldwide. Environmental factors affect GC from the aspects of water, soil, air, radiation, and geology. Risk factors identified include water type, water pollution, water hardness, soil type, soil pollution, soil element content, climate change, air pollution, radiation, altitude, latitude, topography, and lithology; and most of them have an adverse impact on GC. Furthermore, we found that their effects followed five common rules: (1) the leading environmental factors that affect GC incidence and mortality vary by region, (2) the same environmental factors may have different effects on GC in different regions, (3) some different environmental factors have similar effects on GC in essence, (4) different environmental factors often interact to have combined or synergistic effects on GC, and (5) environmental factors can affect human factors to have an impact on GC. Environmental factors have a great impact on GC. Human beings may prevent GC by controlling carcinogenic factors, screening high-risk populations and providing symptomatic and rehabilitative treatments. Furthermore, adaptation measures are recommended to reduce GC risk on private and public levels. Future studies should transcend existing empirical studies to develop causal relationship models and focus on vulnerable population analysis.

The evaluation of HERV-K env, np9, rec, gag expression in normal, polyp and cancerous tissues of gastric and colon

Aim: Gastrointestinal cancer is one of the most alarming cancers worldwide. Infections exert an impact on tumor progression in gastrointestinal tissues. The alteration in the expression of human endogenous retrovirus-K ( HERV-K) genes could remarkably induce oncogenic activity. Materials & methods: In 22 gastric and 23 colon cancer patients, the expression level of HERV-K env, rec, gag and np9 were evaluated. Results: While there was a slight increase in the expression of HERV-K env in colon cancer tissues, the expression level of this gene decreased in gastric tissues. Moreover, the expression of both np9 and gag HERV-K were upregulated only in colon cancer. Nevertheless, rec HERV-K was downregulated in gastric cancer tissues. Conclusion: HERV-K-associated genes can be used as a possible biomarker for cancers diagnosis.

Geospatial analyses identify regional hot spots of diffuse gastric cancer in rural Central America

Background

Geospatial technology has facilitated the discovery of disease distributions and etiology and helped target prevention programs. Globally, gastric cancer is the leading infection-associated cancer, and third leading cause of cancer mortality worldwide, with marked geographic variation. Central and South America have a significant burden, particularly in the mountainous regions. In the context of an ongoing population-based case-control study in Central America, our aim was to examine the spatial epidemiology of gastric cancer subtypes and H. pylori virulence factors.

Methods

Patients diagnosed with gastric cancer from 2002 to 2013 in western Honduras were identified in the prospective gastric cancer registry at the principal district hospital. Diagnosis was based on endoscopy and confirmatory histopathology. Geospatial methods were applied using the ArcGIS v10.3.1 and SaTScan v9.4.2 platforms to examine regional distributions of the gastric cancer histologic subtypes (Lauren classification), and the H. pylori CagA virulence factor. Getis-Ord-Gi hot spot and Discrete Poisson SaTScan statistics, respectively, were used to explore spatial clustering at the village level (30–50 rural households), with standardization by each village’s population. H. pylori and CagA serologic status was determined using the novel H. pylori multiplex assay (DKFZ, Germany).

Results

Three hundred seventy-eight incident cases met the inclusion criteria (mean age 63.7, male 66.3%). Areas of higher gastric cancer incidence were identified. Significant spatial clustering of diffuse histology adenocarcinoma was revealed both by the Getis-Ord-GI* hot spot analysis (P-value < 0.0015; range 0.00003–0.0014; 99%CI), and by the SaTScan statistic (P-value < 0.006; range 0.0026–0.0054). The intestinal subtype was randomly distributed. H. pylori CagA had significant spatial clustering only in association with the diffuse histology cancer hot spot (Getis-Ord-Gi* P value ≤0.001; range 0.0001–0.0010; SaTScan statistic P value 0.0085). In the diffuse gastric cancer hot spot, the lowest age quartile range was 21–46 years, significantly lower than the intestinal cancers (P = 0.024).

Conclusions

Geospatial methods have identified a significant cluster of incident diffuse type adenocarcinoma cases in rural Central America, suggest of a germline genetic association. Further genomic and geospatial analyses to identify potential spatial patterns of genetic, bacterial, and environmental risk factors may be informative.

Environmental etiology of gastric cancer in Iran: a systematic review focusing on drinking water, soil, food, radiation, and geographical conditions

The aim of this systematic review study was to investigate the causal relationship between environmental factors and gastric cancer (GC) in Iran. In a narrow definition, the environment includes water, soil, air, and food. This definition was the main criterion for the inclusion of articles in this study. In addition, exposure to radiation and geographical conditions were considered as less investigated environmental factors in the literatures. International (PubMed, Web of Science, ScienceDirect, Scopus, and Cochran) and national (Scientific Information Database) databases were searched for articles on GC and environmental risk factors in Iran. Twenty-six articles were found to meet the inclusion criteria after title, abstract, and full text review. Risk factors identified for GC include consumption of red meat; high fat, fried, and salted meat; smoked, salted, and fried foods; some dairy products; roasted and fried seeds; strong and hot tea; and un-piped and unchlorinated drinking water, as well as exposure to radiation, loess sediment, soft and grassy soil, soil containing low concentration of molybdenum, and proximity to volcanos. Fresh fruits and vegetable, fresh fish, and honey consumption were recognized as protective agents. Given the risk factors identified, strategies to prevent GC would be educating people to choose a healthy diet and to cook and store food properly, providing access to safe drinking water, taking into account topographical and geographical conditions in choosing a right location to build residential areas, and regulating the use of radiation-emitting devices.

The association of gastrointestinal cancers (esophagus, stomach, and colon) with solar ultraviolet radiation in Iran-an ecological study

Iran has variations in the incidence of cancer in its different provinces. Moreover, it is one of the countries with a high incidence of gastrointestinal cancers in the world. The aim of this study was to investigate the relation between the incidence of esophageal, stomach, and colon cancers with ultraviolet radiation. This is an ecological study. The age-standardized incidence of cancer from 2004 to 2008 was obtained from the National Cancer Registry of Iran for all provinces. UV index data was taken from the world weather site. The altitude and latitude of cities were obtained from the National Topography Organization. Demographic variables were taken from the STEPS report of the Ministry of Health. In this study, lung cancer were used as the index of the effects of smoking. Data were analyzed using the SPSS22 software and through linear regression. UV emission levels showed a strong negative correlation with the incidence of esophageal and gastric cancers, in both genders, in all years. However, this correlation was stronger in men. UV radiation showed a significant correlation with colon cancer among both genders as well. There was no relation between altitude and incidence of cancer. Linear regression results showed that with a unit increase in UV, the incidence of gastric and esophagus cancers in males decreases by β = -4.99 and β = - 3.16 significant coefficients, respectively. Cities with higher levels of UV index have a relatively lower incidence of gastrointestinal cancers. Ultraviolet radiation may act as a protective factor against these cancers.