today , cancer is one of the most important health problems in the world , causing concerns for healthcare systems . new cases of cancer are ever - increasing worldwide , and more than half of the cases are from low and middle income countries . increased exposure to a variety of risk factors and social inequalities are expected to increase the absolute number of cancer cases and their consequences so that an increase of 35% of new cases is predicted in 2020 . in developing countries , lack of equal access to healthcare services and community status , adoption of western lifestyle , and increased old age have led that the burden of cancer has changed during recent decades , and iran is not an exemption from these conditions . cancer , is the third most common cause of death in iran after cardiovascular diseases and car accidents . sadjadi et al . , report that iran is the second country based on mortality rate due to cancer in eastern mediterranean region of world health organization ( who ) . in order to control and reduce morbidity and mortality of cancer and also to carry epidemiological studies , geographical distribution of cancer should be determined as a first step . researchers have demonstrated that a strong link exists between health status and areas where people live in . the characteristics of an area such as , industrial environment , climate , socioeconomic status , lifestyle , and racial groups have a strong effect on cancer incidence and health outcomes . geographic information system ( gis ) is a computer - based system and a potentially powerful assessment tool to represent health data in a visual format by linking statistical and thematic data on maps . it can play a prominent role in helping public health authorities and policy makers for decision - making and planning in epidemiological studies . a review of published literature shows that many studies have been conducted on cancer assessment by using gis in countries . in iran , most of existing literature in this context is on epidemiological studies that have not used spatiotemporal techniques . only a few studies have documented evaluation of geographical variation of cancer incidence by applying gis . this article aims to map the cancer incidence in the counties of fars province , and also to explore the spatial pattern trends or changes of disease during the years 2001 - 2009 . this study was carried out in fars province , which is located in southern iran and has an area of about 122,400 km which is at 27 31 to 31 42 longitude north and 50 37 , to 55 38 latitude east . the total population of fars is about 4.6 million and male to female ratio is 1.03 . the capital city is shiraz , one of the metropolises in iran [ figure 1 ] . map of counties of fars province in this cross sectional study , we used map data , population distribution derived from census and patient data . the new cases were patients diagnosed with cancer whom are registered between 2001 and 2009 among the study population in the cancer registry center of shiraz university of medical sciences . this center use multiple sources ( hospital , diagnostic facilities , and death certification ) ; the data were collected from throughout the province and then to be set up in deputy of health at shiraz university of medical sciences ( cancer registry office ) . also , these were checked by the ministry of health , and then to be sent to this center in shiraz . data sheet included 33,398 patient names , sex , age at the time of diagnosis , place of residence , and cancer diagnosis that was based on the international classification of disease for oncology ( icd - o ) . the documents were checked and any duplicates cases with the same information , cases from the other provinces , unclear diagnosis , and uncertain address were excluded . the final data were summarized in another sheet and included 28,411 new cases and consisted of sex , place of residence , types of cancers , and an eight age - group classification . crude incidence ratio was calculated for each sex and age groups in counties in each year . then , to compare different counties , age - standardized rate ( asr ) was calculated using standard world population . the calculated asrs were transferred to the gis software ( arc gis 9.3 ) , and mapping tools of gis were then used for visualizing asr for each year . we also used exploratory spatial data analysis ( esda ) to determine distribution pattern of cancer for each year of data . one of the most frequently used methods is moran 's index , which evaluates local clustering or spatial autocorrelation by computing the contribution of each location to the moran 's i statistics for the whole study area . moran 's i is a weighted correlation coefficient that takes values in the range ( 1 , 1 ) . if value of moran 's i is a significant positive value , it indicates positive spatial autocorrelation , which means , a distribution pattern for counties having asr similar to their neighboring counties . a significant negative value is negative spatial autocorrelation , meaning there is no similarity between neighbors . moreover , we used the local indicators of spatial association ( lisas ) measure in positive moran 's i , to identify meaningful spatial clusters ( p = 0.05 ) . lisa analysis was typically mapped to indicate counties with similar asr ( high , low ) among various areas . asr calculation was performed in microsoft excel , spatial and temporal analyses were performed using arc gis 9.3 and geoda 1.0.1 . a total of 28,411 new cases were diagnosed with cancer in 2001 - 2009 in fars , 15,759 ( 55.5% ) of which were men . the average age of cases was 61.6  0.5 year , and it breaks down to 63.8  0.6 for men and 58.8  0.8 for women . the averages asr were 102.17 and 82.17 per 100,000 among men and women , respectively . the highest asr among men was 148.82 per 100,000 , observed in 2007 , whereas for women , the highest value was 114.80 per 100,000 in 2009 [ figure 2 ] . age - standardized rate in men and women in fars province , iran , during 2001 - 2009 table 1 shows asr in counties of fars province that the highest value is shiraz among all years . age - standardized rate in counties of fars province , iran , during 2001 - 2009 to illustrate the geography of cancer , asr distribution of the study region is plotted in figure 3 . darker brown signifies a higher asr value , and the men to women ratio for cancer is also symbolized in figure 3 . it is clear that in most of the counties , cancer incidence was more in men than women for various years , but the proportion of women has increased in 2009 . it can also be observed that asr showed a much dispersed distribution pattern in 2001 with three areas of high concentration , namely shiraz , marvdasht ( northern fars ) , and larestan ( southern fars ) in the following years ( except 2002 ) . the scattering was much less and the proportion of each cities increased , but consistently shiraz , marvdasht , and larestan had a high density in each year . in 2002 , asr decreased throughout the province . spatial distribution of cancer in the counties of fars , during 2001 - 2009 these findings are supported numerically using moran 's i , shown in table 2 , where it is seen that in 2001 moran 's i is negative , meaning that pattern of cancer incidence was dispersed . the spatial distribution tends to cluster in subsequent years , and moran 's i becomes significant positive for three consecutive years ( 2004 , 2005 , and 2006 ) as shown with the p value . however , moran 's i decreased again and the distribution changed to a clustered pattern in the end of the period . moran 's index of asr , 2001.2009 ( p=0.05 ) geoda software was utilized to determine significant spatial clusters in certain years . the findings were showed high - high cluster on shiraz , sepidan , mamasani , nayriz , arsanjan , khorrambid , bavanat , and zarrindasht that represent high asrs are surrounded by those which also have high asr . cancer incidence was dispersed in the first year ( moran 's i = 0.002 and 0.006 ) and in 2004 , 2005 , and 2006 had significant moran 's i and spatial clusters , while distribution pattern of cancer was diffuse in the next years . counties with similar asr were geographically closer to one another in the periods of cluster . spatial distribution of cancer in the male , during 2001 - 2009 lower incidence of cancer was observed in the women for the period 2001 - 2003 in the smoothed maps [ figure 5 ] . the spatial dependency of cancer in women was clustered in 2004 , 2005 , and 2006 at the significance level of 0.05 , so that most of the density was located in shiraz , larestan , and their neighboring areas . the overall global burden of cancer is increasing , so that cancer incidence , diagnostic and treatment facilities , and cancer control programs exist differently in various geographic boundaries of the world . differences in cancer incidence rate were shown in the iranian population in the recent years . our study estimated average asr of 102.17 and 82.17 per 100,000 persons in men and women , respectively , while in comparison with the findings of masoompour et al . , and mehrabani et al . , have increased incidence and age of illness onset . also , the finding is comparable with studies performed in semnan and kerman provinces . sadjadi et al . , showed that in kerman province , ( neighboring fars province ) asr was 76 and 68 in men and women , respectively , while our findings showed higher rates . in 2002 and also some of counties in other times , the obtained low cancer incidence rate was probably due to incomplete registered data ( incomplete forms for residence cities of patients ) . overall , cancer increase trend in the present study , maybe related to aging of the population . one of the most important contributing factors to increasing cancer occurrence in the world is due to increased life expectancy and aging of the population . cancer incidence was higher in the men than women , perhaps due to increase the specific cancers in men , or being exposed to identified risk factors such as smoking , using alcohol , occupational carcinogens and other agents . the mean age of women who developed cancer was lower compared to men , which can be explained by increasing detection with screening tests ( pap smear and breast examination ) , performed in the health care centers . however , women are more concerned about their health , and as a result they visit physicians relatively more , this might result in an earlier detection of cancer . asr of shiraz and larestan were higher than neighboring cities during years , that maybe due to lifestyle , exposure to industrial pollution , migration of various races and people and influence of genetic and life traditions . moreover , some patients may move to large cities in order to have better access to more equipped facilities for diagnostic and treatment measures , which can be considered a confounding agent . also , lack of proper surveillance systems in some health care centers in the underprivileged and small cities can affect our findings . the level of knowledge and attitude of people about health promotion and preventive activities of chronic diseases like cancer may affect distribution of cancer . in most of southern regions of fars with low population density , cancer incidence trend was increasing , and it is expected that , asr will rise even more in future . therefore it should be a priority for health policy makers for development and implementation of comprehensive cancer control programs . epidemiological studies should be considered for determining important roles of climate and geographical condition in cancer incidence . the study was conducted in trabzon , turkey ( yomralioglu et al . ) showing that incidence of some cancers have been different in various geographical locations . while epidemiology of cancer incidence using gis has been well studied in developed countries , it has not received adequate attention in developing countries . a review of published studies , we did not find cancer study using gis in fars province . the study was conducted to determine clustering of childhood cancer in tehran , another was to assess pattern of spread of gastrointestinal cancer in the caspian sea region . the obtained moran 's i in 2004 , 2005 and 2006 show that the distribution of cancer was more regular than other years and spatial clusters were found in shiraz , sepidan , mamasani , nayriz , arsanjan , khorrambid , bavanat and zarrindasht . the clustered patterns suggest that contributing factors may be similar in the mentioned counties , which can be surveyed in future epidemiological studies . gis can be used effectively for assessment of cancer incidence , in the geographical location and to provide insights for placing control measures . of course , researchers should consider although maps help to visually evaluate spatial pattern , they have limitations . wainwright et al . , collected cancer data in maryland , usa , and analyzed effects of different variables such as population , income , unemployment indicator , and urban and rural areas . this is not possible in our study due to lack of access to accurate information such as socioeconomic conditions . the spatial analysis by gis is a method that is feasible and helpful in generating hypothesis and identifying areas for intervention . it could be necessary and important for public health policymakers to promote strategies for cancer control and management for infrastructure . therefore , knowledge of spatial distribution of cancer is expected to provide accurate and easily accessible information for implementation of preventive activities in community health . our study showed spatial analysis of cancer incidence and clustered pattern in the fars province over a period of time . further studies are needed on the efficiency of gis , not only to determine etiological agents of cancer but also to help policy makers in management of health promotion .
background : cancer is a major health problem in the developing countries . variations of its incidence rate among geographical areas are due to various contributing factors . 
 this study was performed to assess the spatial patterns of cancer incidence in the fars province , based on cancer registry data and to determine geographical clusters.methods:in this cross sectional study , the new cases of cancer were recorded from 2001 to 2009 . 
 crude incidence rate was estimated based on age groups and sex in the counties of the fars province . 
 age - standardized incidence rates ( asr ) per 100,000 was calculated in each year . 
 spatial autocorrelation analysis was performed in measuring the geographic patterns and clusters using geographic information system ( gis ) . 
 also , comparisons were made between asrs in each county.results:a total of 28,411 new cases were diagnosed with cancer during 2001 - 2009 in the fars province , 55.5% of which were men . 
 the average age was 61.6  0.5 years . 
 the highest asr was observed in shiraz , which is the largest county in fars . 
 the moran 's index of cancer was significantly clustered in 2004 , 2005 , and 2006 in total , men , and women . 
 the type of spatial clustering was high - high cluster , that to indicate from north - west to south - east of fars province.conclusions:analysis of the spatial distribution of cancer shows significant differences from year to year and between different areas . 
 however , a clear spatial autocorrelation is observed , which can be of great interest and importance to researchers for future epidemiological studies , and to policymakers for applying preventive measures .