Variability of cancer risk within an area: time to complement the incidence rate

Incidence Pattern and Geographical Distribution of Breast Cancer among Females Using Geographic Information System in Kermanshah Province, West Iran: First Data from A Population-Based Cancer Registry in Kermanshah

Background: Breast cancer (BC) is the second most frequent cancer in females worldwide. In recent years, the incidence rates of BC have been increasing among Iranian women. This study aimed to examine the incidence of BC among females in Kermanshah province, west of Iran, based on the data taken from the Kermanshah Population-based Cancer Registry (KPCR) during 2014-2017. Methods: In this registry study, data were obtained from the KPCR, a high-quality cancer registry that collects data on various cancers using standard protocols all over Kermanshah province. The crude incidence rates (CRs) and age-standardized incidence rates (ASRs) of BC were determined per 105 person-years. Further, temporal trends were assessed using joinpoint regression analysis to describe the average annual percent change (AAPC) and 95% CIs. ArcGIS software was used to map the geographic distribution of BC incidence. Results: During 2014-2017, 1,177 new cases of BC were detected in Kermanshah province. Most of the females diagnosed with BC (cases/100,000, percentage) lived in Kermanshah county (900, 76%) compared to the other counties (277, 23%). The overall ASR of BC increased by 38.7 cases per 100,000 females-year (AAPC: 2.2; 95%CI 5.1-10.1; P=0.3). The lowest and highest ASRs were observed in 2015 (36.7/100,000) and 2017 (40.7/100,000), respectively. The maximum incidence of BC among females was reported in the age group 45-49 years. Conclusion: The BC trend for females increased from 2014 to 2017 in Kermanshah province across all age groups, especially in the age group 45-49 years. Thus, it is essential to take a series of effective health measures to prevent and control this cancer.

Variation of Cancer Incidence between and within GRELL Countries

Variation in cancer incidence between countries and groups of countries has been well studied. However cancer incidence is linked to risk factors that may vary within countries, and may subsist in localized geographic areas. In this study we investigated between- and within-country variation in the incidence of all cancers combined for countries belonging to the Group for Cancer Epidemiology and Registration in Latin Language Countries (GRELL). We hypothesized that investigation at the micro-level (circumscribed regions and local cancer registry areas) would reveal incidence variations not evident at the macro level and allow identification of cancer incidence hotspots for research, public health, and to fight social inequalities. Data for all cancers diagnosed in 2008–2012 were extracted from Cancer Incidence in Five Continents, Vol XI. Incidence variation within a country or region was quantified as r/R, defined as the difference between the highest and lowest incidence rates for cancer registries within a country/region (r), divided by the incidence rate for the entire country/region × 100. We found that the area with the highest male incidence had an ASRw 4.3 times higher than the area with the lowest incidence. The area with the highest female incidence had an ASRw 3.3 times higher than the area with the lowest incidence. Areas with the highest male ASRws were Azores (Portugal), Florianopolis (Brazil), Metropolitan France, north Spain, Belgium, and north-west and north-east Italy. Areas with the highest female ASRws were Florianopolis (Brazil), Belgium, north-west Italy, north-east Italy, central Italy, Switzerland and Metropolitan France. Our analysis has shown that cancer incidence varies markedly across GRELL countries but also within several countries: the presence of several areas with high cancer incidence suggests the presence of area-specific risk factors that deserve further investigation.