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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 9  |  Issue : 1  |  Page : 89-93

National distribution of stomach cancer incidence in Iran: A population-based study


1 Pediatric Developmental Disorders Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
2 Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
3 Department of Epidemiology, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
4 Department of Public Health, School of Public Health, Dezful University of Medical Sciences, Dezful, Iran
5 Department of Community Medicine, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran
6 Department of Health Education, School of Public Health, Hamadan University of Medical Sciences, Hamadan, Iran
7 Department of Epidemiology, School of Public Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
8 Research Center for Environmental Pollutants, Department of Epidemiology and Biostatistics, Qom University of Medical Sciences, Qom, Iran

Date of Web Publication4-Jan-2019

Correspondence Address:
Shahrzad Nematollahi
Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/AIHB.AIHB_37_18

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  Abstract 


Backgrounds and Aims: Stomach cancer (SC) is the fourth most common cancer and the second leading cause of death due to cancer in the world. The aim of this study was to investigate the provincial distribution as well as age-specific incidence of SC in both genders across Iran. Materials and Methods: This ecological study was conducted according to re-analysis of medical records aggregated to provinces from National Registry of Cancer and Disease Control and Prevention report of the Ministry of Health and Medical Education for SC in 2008. For each province, the average annual age-standardised rate (ASR) for the incidence of SC was calculated. Results: Our findings showed that in Iran, adenocarcinoma, not otherwise specified, was the most common histological type of SC in both genders (59% in males and 56% in females), while intestinal type of adenocarcinoma had the lowest prevalence (14% in males and 12% in females). In age groups above 45 years, there was a steady upward trend, and the highest ASR in both genders was related to 80–84 years of age with 292.14 and 112/100,000 in males and females, respectively. Conclusion: The assessment of geographical distribution showed that there is a wide geographical variation in the incidence of SC across the 31 provinces of Iran, and the ASR of SC in South-East and North-West parts of Iran was higher than any other areas. Thus, development access to screening services and carryout of prevention programs should be considered for high-risk groups in these areas.

Keywords: Epidemiology, incidence, Iran, stomach neoplasms


How to cite this article:
Jenabi E, Saatchi M, Khazaei S, Mansori K, Ayubi E, Soheylizad M, Khazaei L, Nematollahi S, Beigi AM. National distribution of stomach cancer incidence in Iran: A population-based study. Adv Hum Biol 2019;9:89-93

How to cite this URL:
Jenabi E, Saatchi M, Khazaei S, Mansori K, Ayubi E, Soheylizad M, Khazaei L, Nematollahi S, Beigi AM. National distribution of stomach cancer incidence in Iran: A population-based study. Adv Hum Biol [serial online] 2019 [cited 2020 Aug 15];9:89-93. Available from: http://www.aihbonline.com/text.asp?2019/9/1/89/243757




  Introduction Top


Despite the dramatic decrease in stomach cancer (SC) incidence and mortality over 70 years,[1] it is still the fourth most common cancer and the second leading cause of death due to cancer worldwide.[2] Adenocarcinoma tumours comprise most of SC malignancies which are further divided into intestinal (e.g., well differentiated) and diffuse (e.g., undifferentiated) subsites. Apart from different types of stomach atrophy they induce, the two types of SC have different epidemiology as well. The intestinal SC is more frequent in high-risk geographic areas, males, blacks and the elderly,[3] whereas diffuse SC occurs in uniform geographic distribution and has a less gender variation.[4] Declined incidence of SC has been mostly due to intestinal SC occurrence, while on the other hand, incidence of diffuse SC, particularly the signet ring type, had been increasing.[5]

The incidence of SC is strongly influenced by several exogenous and endogenous factors, mostly unknown. The exogenous factors such as food conservation and additives, Helicobacter pylori infection and low socioeconomic status are predominant in high-incident areas.[6],[7]

Conversely, in low-incident areas, endogenous factors such as family history of SC or colon and blood type A are more influential. Nonetheless, most influential determinants of globally fallen incidence of SC have been attributed to changes in exogenous factors.[8] In other words, improving living standards and dietary habits, as well as reduction of H. pylori infection are amongst the major changes which experiences the world.[3]

This study aimed to describe the provincial distribution as well as age-specific incidence of SC in both genders across Iran. Findings of this study can help policymakers and planners for better resource allocation and management of screening programs and apply treatment strategies for various provinces across Iran.


  Materials and Methods Top


In this ecological study, we used medical records aggregated to provinces from National Registry of Cancer and Disease Control and Prevention report of the Ministry of Health and Medical Education for SC in 2008.[9] Data collection by the Iranian Cancer Registry is active and pathology based and covering the whole country's pathology laboratories. Hospital-based and death certificate-based data have not been included. Cleaned data from province after deleting for repeated cases were transmitted to the Ministry of Health and Medical Education every 3 months. Process of data collection of cancer cause in Iran is presented in [Figure 1].
Figure 1: Process of data collection of cancer cause in Iran.

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Registered data were classified into three parts as follow: (1) patient's identity characteristics including age, gender, race and residence location, (2) patient's clinical history and (3) preclinical findings. Data on the primary location of tumour, cancer diagnosis date, morphology and histology and diagnosis method are registered.

For each province, the average annual age-standardised incidence rate (ASR)/100,000 person-years was calculated by the direct method using the world standard population.[10] The data were presented using MS Excel 2010. ArcGIS 10.4.1 (ESRI, Redlands, CA, USA) was used for mapping the incidence of SC per province.


  Results Top


Overall, 5240 cases with SC had been registered in 2008. Assessment of geographical distribution of the cases showed that SC occurred most frequently in West-North and East-North of Iran. In addition, it occurred more frequently in some central provinces such as Yazd and North-West parts such as East Azerbaijan [Figure 2] and [Figure 3]
Figure 2: Geographic distribution of stomach cancer incidence rate in Iran according to gender in 2008, males.

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Figure 3: Geographic distribution of stomach cancer incidence rate in Iran according to gender in 2008, females.

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In both Iranian men and women, adenocarcinoma, not otherwise specified (NOS), was recorded as the most common form of SC (59% in males and 56% in females), while intestinal type of adenocarcinoma had the lowest prevalence (14% in males and 12% in females) [Table 1]. We found that age–sex-specific incidence of SC formed asymmetric pyramid in a way that it occurred more quickly after 45–49 years old. The highest increase in incidence was 292.14 in men and 112 in women of 80–84 years old [Figure 4].
Table 1: Incidence of different subsites of stomach cancer in Iran according to gender in 2008

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Figure 4: Age-sex pyramid of stomach cancer incidence rates in Iran in 2008.

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Occurrence of age-standardised rate (ASR) of SC in Iranian men was highest in West Azerbaijan (30) and lowest in Sistan and Baluchestan (3.8). On the other hand, it occurred most frequently in Ardabil (14.2) and least frequently in Bushehr (1.7). West Azerbaijan Province experienced the highest age-adjusted incidence rate (ASR) of SC in males (ASR: 30), while this ranking was slightly different in Iranian females such a way that the first three provinces with the highest ASR in females were Ardabil (14.2), West Azerbaijan[11] and Gilan (11.7) [Table 2].
Table 2: Province-wide age-standardised incidence rate of stomach cancer in Iran, in 2008

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  Discussion Top


Our results showed that all types of SC (e.g., adenocarcinoma, adenocarcinoma NOS and signet cell ring) were more reported amongst men. In age groups above 45 years, there was also a steady upward trend. It has been shown that males have a genetic predisposition towards SC.[11],[12] Moreover, amongst several explanations for greater frequency of SC in Iranian men, smoking plays a significant role. Despite the low fraction of SC cases attributed to smoking (10%), major differences in smoking prevalence in Iran which is mainly a man's behaviour may also be important.[13]

The combination of male gender and older ages can be further modified by H. pylori, a Gram-negative bacillus which strongly affects the pathology of SC worldwide.[14] The increase in prevalence of H. pylori infection with age is largely due to a birth cohort effect. H. pylori infection is mainly acquired during early childhood, and infection persists lifetime. The higher presence of SC in older ages in Iran can be justified by the established link between chronic H. pylori infections with SC.[15] Nevertheless, H. pylori infection had been linked to the risk of non-cardia SC,[16] while we found that the most common subsite of SC cases in Iran was adenocarcinoma, for example, the non-cardia form of SC. This increase is mainly due to rising in the gastroesophageal reflux disease associated with the obesity epidemic.[17]

It is unlikely that H. pylori infection alone is responsible for the development of SC. Rather, H. pylori may produce an environment conducive to carcinogenesis and interact with other lifestyle and environmental exposures such as dietary behaviours and smoking habits. There is evidence that consumption of salty foods and N-nitroso compounds and low intake of fresh fruits and vegetables.[3]

Iran has been undergone tremendous changes in terms of population aging, urbanisation and social transformation which put Iran as a medium level of human development index followed by great changes in cancer patterns.[18] We found that in Iran, North-West parts of the country had the highest age-standardised incidence rate, while this quantity was lowest in South and South-East parts. Geographic distribution of SC can be mainly due to distinct patterns of dietary habits, smoking behaviours and socioeconomic status.[4],[19]

Some increase in reports of SC cases, although could be related to the improvement in histologic diagnostic tools for oesophagus and stomach malignancies.[20] Scrutiny of trends in cancer incidence through population-based cancer registries is an indispensable tool for providing data for planning and evaluation of programs for cancer control.[11] Avoidance of food preservation, salt intake and decreasing initiation and cessation of smoking can be regarded as preventive measures for SC.[21]

Due to paucity of data supporting screening for SC, there is currently no regular practice for it in most Asian countries.[14] Expert consensus indicates that there should be a cut-off age for SC screening, with optimum age of 40–45 years, men and first-degree relatives of SC patients.[14]

Being cost-effectiveness of endoscopy screening, biannual for high-risk populations has been approved by a study from Singapore.[22] Mass eradication of H. pylori in the community has been proposed as an alternative to mass screening in SC. This strategy has extra advantage for young patients <30 years of age.[14] Several studies on two strategies of screening for H. pylori and treatment of those positive with no screening and no treatment showed that there is a potential cost-effectiveness for screening and treatment of H. pylori in high-risk populations.[14],[23],[24] However, concerns regarding overuse of antibiotics and emergence of resistant strains of the pathogen are on the rise.[20]


  Conclusion Top


We found that men, advanced ages and South-East and North-West parts of Iran are in greater risk of SC occurrence. Identification of high-risk groups can influence the effectiveness of preventive measure significantly. Recommendations regarding screening of these groups have been suggested.

Some limitations should be addressed towards of the current study; first, we did not have access to data regarding cancer stage at diagnosis time in order to conduct a more detailed investigation. Second, we did not have data on age average according provinces.

Acknowledgements

The authors would like to thank the National Cancer Department staff at the Ministry of Health and Medical Education for providing data for the research of cancer epidemiology in Iran.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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An international association between Helicobacter pylori infection and gastric cancer. The EUROGAST study group. Lancet 1993;341:1359-62.  Back to cited text no. 15
    
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El-Serag HB. Time trends of gastroesophageal reflux disease: A systematic review. Clin Gastroenterol Hepatol 2007;5:17-26.  Back to cited text no. 17
    
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    Figures

  [Figure 1], [Figure 2], [Figure 3, [Figure 4]
 
 
    Tables

  [Table 1], [Table 2]


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