Epidemiologic pattern of cancers in Iran; current knowledge and future perspective

Abstract

Iran is a developing country facing demographic transition. Cancers are among the major non-communicable disorders with remarkable budern on the health-care governing systems. Extended life expectancy of Iranian population, change in living style, as well as promoted diagnostic and treatment methods have resulted into significant malignancies emergence and detection. Understanding the trend of this epidemiologic transition is required for proper allotment of resources. In this manuscript, overall epidemiologic pattern of cancers and their burden transition is reviewed. In addition, more concerning neoplasia (gastrointestinal, breast, thyroid, urologic, and respiratory system cancers) are reviewed in more details.

Iran, as a developing country, is facing a major demographic and epidemiologic transition. This transition is mainly comprised of a burden shift from communicable etiologies toward non-communicable diseases (NCDs) among which cancers place a considerable burden on the governing health system [1], being the 3rd cause of death in Iran nowadays [2]. The emergence of national mortality and cancer registries has facilitated evaluation of the burden of different cancers and diseases [3, 4]. National and Sub-national Burden of Diseases (NASBOD) as an interactive and open-access method to describe and compare the burden of various pathologies has been a big step forward in regard to understanding the impact of each entity in national and subnational scales [5–7]. A similar effort for estimation of epidemiologic parameters has been undertaken by the Institute for Health Metrics and Evaluations (IHME) [8].

In Iran, It has been demonstrated that deaths due to cancers follow a reverse-U pattern [6] and are decreasing nowadays [9]. Crudely, in 2015, around 36,500 persons recorded to die of all cancers taken together. The highest deaths in NASBOD were for the year 2001 with roughly 44,000 records [6]. Based on NASBOD, the highest recorded death-rate of this lethal diagnosis was in 1996, with a value of 71.7 per 100,000 persons in both sexes. Neoplasms crude and standardized death rates follow same patterns, though standardized death rates had a more pronounced downward slope [6]. In 2015, it is reported that 45.4 deaths have occurred because of cancers in every 100,000 Iranian population [6]. Considering genders, 55.0 deaths has been ensued in 100,000 males, compared to 35.8 in female counterparts [6]. IHME claims that in 2017, a total of 133,627 (119,260 – 150,706) new incident cases of neoplasms have been diagnosed in Iran; with a standardized rate of 162.6 (145.1 – 183.3) per 100,000 person-years. Malignancies are major sources of Disability-Adjusted Life Years (DALYs) [10] — as the main indicator of burden — in every nation or region. Based on IHME, in 2017, a total of 1,589,265 (1,477,635 – 1,638,433) DALYs have been attributed to cancers in Iran with a standardized estimate of 1934 (1798 – 1993) [8] years. The prevalence of neoplasms is steeply increasing in most countries, and developing ones harbor a more profound increment [11]. There existed 624,818 (562,365 – 657,648) patients living with cancer in Iran in year 2017 [8]. Of 100,000 people living in Iran in 2017, 760 (684 – 800) persons had cancer. These values have almost doubled of the year 1990, providing insight on the extent of the abovementioned epidemiologic transition.

In 90s, leukemias, stomach, and brain cancers were the most burdenous neoplasia of females in Iran [6, 8]. Leukemias, stomach, and respiratory cancers were the most burdensome malignancies of males in Iran. Improvements in diagnostic and screening techniques and treatment modalities has yielded a fundamental change in the composition of human cancers. In 2017, breast cancer has supervened the stomach and thyroid cancers in females while it has almost remained in same order in male population [8]. Following is a detailed epidemiologic trends and description of major cancers in Iran.

Gastrointestinal cancers

Epidemiologically, colorectal cancers are the fastest growing neoplasms. In Iran, in 1990, this group of cancers were the 7th and 25th sources of DALYs in males and females respectively; while in 2017 being the 4th for both genders [8]. Colorectal cancers make up the third most prevalently discovered cancer in males and second in females [12]. Change in diet toward processed foods as well as introduction of new methods of screening are the reasons for the rising burden of this group of cancers [13, 14]. Unlike other common neoplasms [15], death-rate due to colorectal cancers has gone through a rising path [6]. In early 90s, the mortality rate was 2.87 (2.4 – 3.5) in 100,000 and increased almost twice to 6.8 (6.0 – 7.1) in 2017 [8, 16]. There seems to be a relation between the development status of a nation and incidene of colorectal cancers [17].

Worldwide, stomach cancer is the 5th prevalent cancer and 3rd source of cancers death. The incidence rate of stomach cancer among both males and females had an increasing trend and it increased by 2.3 and 0.8 persons for every succeeding year, respectively [18]. There has been estimated that 11.9 (11.5 – 12.4) new incident cases of stomach cancers emerged in Iran in 2017 compared to 8.1 (7.8 – 8.4) in 1999 [8]. On the other hand, deaths due to stomach cancer is decreasing [6]. In 2015, 8.0 deaths has occurred in every 100,000 Iranian national residents compared to 13.9 in 1999 [6]. In contrast to the colorectal cancer, stomach cancer is inversly associated with the development status of a country [19].

Pancreatic and liver cancers are other less prominent cancers of gastrointestinal system with incrasing burdens worldwide. In Iran, pancreatic cancers had 4.1 (3.9 – 4.3) death-rates in 2017; compared to 2.2 (2.1 – 2.5) in 1990, it has almost doubled in this period. While increasing abruptly, Iran has a lower mortality rate compared to other nations with similar sociodemograhic properties [10]. Similarly, Liver cancer’s standardized death-rate increased from 1.1 (0.8 – 1.6) in 100,000 persons in 1990 to 5.6 (4.2 – 7.6) in 2015 [20]. Increasing rates of alcohol consumtion and infections in addition to ageing of Iranian population are the suggested blueprints of the rising burdens of these two exocrine glands of human gastrointestinal system [10, 20]. Controlling for dietary behavior and education toward mere screening strategies and adoption of vaccination programs are required to deal with gastrointestinal cancers.

Breast cancer

Globally, it is believed that breast cancer is the most common cancer with estimated prevalence of 2.4 million (2.3 – 2.5 million) living cases in 2015 [19]. A systematic review performed on the literature in regard to epidemiologic aspects of breast cancer in Iran has revealed an incidence rate of 22 in 100,000 Iranian women [21]. The age-group 40–49 were the group with most incident cases [21] and is emphasized that women in Iran are affected 10 years earlier than other women around the world [22]. In 2017, it has been estimated that 351.3 (275.2 – 374.2) DALYs were atribuated to breast cancer in Iran; being almost twice as stomach cancer and 30-times of thyroid cancer [8]. Unfortunately, 71% of patients are discovered in advanced stages and two-thirds require extensive treatments [23]. In a national scale, about 2 in 100,000 women die of breast cancer each year, while the trend is downsloping. Through a population based-study, it has been demonstrated that 61% of general Iranian women know about breast cancer and the screening programs; while only 17% reported performing regular screening and examination [24]. Indeed, the focus of primary health care providers should be to raise the awareness about breast care among women.

Respiratory system cancers

Lung cancer in Iran is found less commonly than western countries. It has been suggested that smoking is the main risk factor for this type of malignancy. The main reason for lower incidence of lung cancer in Iran may be attributed to the fact that the rate of smoking, especially in females, is lower than other parts of the world [17]. While it should be mentioned that the incidence rate of the respiratory system cancers (trachea, bronchus, and lung) are increasing steeply. In 1990, the incidence rate has been estimated to be 4.4 (4.0–4.9) in 1990 and rose to 8.7 (8.4–9.1) in 2017 [8]. These cancers have been the second source of DALYs in males and fifth in females in year 2017 [8]. Western provinces of Iran have higher incidence rates despite this cancer; this notion might be a result of higher dust and air pollutants found in these regions [25]. Controlling for air pollutants and smoking behaviors are required in order to confront the burden of this group of cancers.

Other cancers

Thyroid cancer is the most prevalent endocrine malignancy of human body [17]. Before administration of iodinated salts, Iran was an endemic site of thyroid cancer [26]. Diagnostic and screening programs and preventive efforts have led to significant mortality decline and incidence rise in last decades. The death rate has decreased from 552.1 (540.3 – 564.1) in 100,000 persons in 1990 to 462.4 (460.0 – 464.6) in 2017 [8]. In contrary, the incidence rate of this cancer has increased from 0.005 (0.000 – 0.247) in 1990 to 7.8 (4.3 – 13.7) in 2010 in 100,000 Iranian persons. It is worth mentioning that thyroid cancers are found more commonly in females (×2.5) than males [27]. The huge rise in incidence of thyroid cancer is mainly due to vast employment of ultrasound and other means of thyroid cancer and nodules evaluation which their usefulness are not yet reported [28].

Urologic cancers are among the rising burdens of nowadays [29]. In 2016, there were 0.2 (0.2 – 0.3) and 2.7 (2.3 – 3.3) age-standardized deaths due to testicular and bladder cancers in Iran, respectively. While they have low rates of death, DALYs directed to these conditions are significant, with 3288 (2522 – 4284) and 25,158 (20,589 – 31,077) DALYs in the same year, respectively [30, 31]. Similarly, 0.9 (0.7 – 1) and 4.1 (3.0 – 4.5) deaths have resulted from renal and prostate cancers in 2017, respectively; which are 2–3 fold more than 1990 [8]. This rise in burden of urologic cancers is manily amid to the populations growth and ageing [29].

Conclusion

Demographic and epidemiologic transitions follow a logistic growth pattern, with an expansion phase upcoming stationary phase [32]. It seems that Iran has passed the expansion phase and is in the midst of the stationary phase [33]. Combined, going into the stabilized stages of demographic transition opens a window of opportunity for health governing officials to settle executive legislations to better control the current and upcoming burden of NCDs in the fast senescing Iranian population [34].

Authors’ contributions

EM prepared the first manuscript. AA, NF, SA, NR, and YF helped in the process of literature review. NR, SN, FF, and BL reviewed and commented on the final manuscript. NR and BL were the corresponding authors and supervised all stages of manuscript preparation and publication.

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No conflict of interest or competing interest is declared by the authors.

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