The current study has reported the cancer incidence trends from 2013 to 2019 and predicted new cases over the next decade. The overall cancer incidence rate increased sharply during 2013–2014 in both Erbil and Duhok governorates. A plausible explanation for this increase could be due to the demographical changes in the Erbil population as the result of the ISIS invasion of Mosul governorate in 2014, which caused thousands of internally displaced persons to migrate to Khazer refugee camp in Erbil, which led to the detection of a further increase in cancer cases. Thus far, previous studies focused on risk factors such that directly influence the incidence rate of cancer diseases in Iraq, such as the consequence of various wars, changes in the lifestyle 6, the economic disease burden 7, economic crisis 8, social status 9, environmental pollution, and exposure to carcinogenic agents. Moreover, some behavioural factors like smoking, alcohol consumption, drug abuse, and fast food consumption have recently been shown to significantly increase the risk of certain cancers in KRG 9–11.
According to the prediction of the current study for the next decade, there will be a significant increase in cancer burden in Erbil and Duhok governorates. This is in agreement with previous national studies on different types of cancer diseases 2,12−14, as well as international trends that estimated an increase of 28% globally between 2006 and 2016 1. Correspondingly, cancer incidence trends in less developed countries have been expected to increase from 56% in 2008 to more than 60% in 2020. In contrast, in the US and many Western countries, the trends are generally expected to be dropping 11.
The cancer incidence rates in the KRG, particularly in Erbil and Duhok governorates, spiked dramatically between 2013 and 2019; this is partly a structural factor due to the increasing Kurdish population. However cancer incidence rates for all cancer types in the KRG during these periods are lower compared to neighbouring countries or Europe, East Asia, and the US 15, which is likely associated with the lack of implementing evidence-based cancer control programs and planning, which are fundamental for high-quality cancer data registry, but which are almost totally unavailable 16 in most low- and middle-income countries, including KRG. The incidence and burden among both sexes between 2013 and 2019 saw a two-fold increase in Erbil and Duhok governorates for all cancer types. The reason for this drastic increase is likely due to various risk factors, including population growth, ageing, unhealthy lifestyle behaviours, insufficient physical activity, infectious agents, genetic mutations and environmental risk factors 17–19.
Nevertheless, the ratio of cancer rates in females was slightly higher among females compared to males in Erbil and Duhok governorates. A higher percentage in cancer rates in females is most likely due to a great extent, reflect contrasts in endogenous hormones and natural exposures to indoor and outdoor pollution, as well as sophisticated intuitive between these impacts 20.
In Erbil and Duhok governorates, the most frequently documented cancer among females was breast cancer between 2013 and 2019, followed by blood cancer, then colorectal and lung cancer in Erbil and Duhok governorates. The most frequently documented cancer among women in both governorates was breast cancer between 2013 and 2019, followed by blood cancer, colorectal and lung cancer. The most common cancer aligns with cancer incidence trends worldwide. However, the second, third, and fourth most common cancers in the world are colorectal, lung, and cervix uteri, respectively 3. The most prominent risk factor for getting breast cancer is the female gender 21, followed by age, reproductive factors, long history of menstruations, age of the females giving birth to their first child, and elevated use of oral contraceptives, especially in Middle East countries, including Iraq 22. The highest prevalence of female breast cancer in Western countries is between the ages of 75 and 79 years, while in KRG it is between the ages of 51 to 60 years; this indicates that breast cancer occurs in women in this population at a younger age, as in the neighbouring country of Iran, and unlike women in Western countries 22,23.
The most commonly diagnosed cancer in men is lung cancer in Erbil and Duhok, which this aligns with the most diagnosed cancer type in the world. Globally, smoking is the leading cause of death among lung cancer patients, accounting for about 80% of cancer deaths among men 22,23. The reason behind the higher prevalence of lung cancer in Duhok compared to the Erbil governorate could partially be caused by unventilated gasoline-fuelled stoves, indoor kerosene heaters, and fumes from cooking 24; another notable risk factor is an increase of tobacco smoking among women in this governorate. In Erbil, lung cancer ranks fifth place for overall cancer rates in this area, which might indicate that women are smoking less than men and are less exposed to outdoor industrial pollution. However, lung cancer among women is comparable to global lung cancer incidence for 2018 15.
The second most diagnosed cancer during seven years of cancer registry in the KRG is leukaemia, which was slightly higher in males than in females. Leukaemia is a relatively less common diagnosed cancer worldwide 25, and the first leading cause of death in the Sulaymaniyah governorate of KRG between 2006 and 2013, as reported by Khoshnaw et al. 13. It is likely that three major destructive wars in Iraq since 1980 have resulted in the presence of significant volumes of military pollution throughout Iraq, including depleted uranium (DU), which are widely suspected of causing a significant increase in congenital disabilities and cases of cancer, particularly childhood leukaemia 26,27.
The third most commonly diagnosed cancer among men in both governorates is kidney cancer, for which incidence rates among men were nearly three to four times higher than among women in the Erbil governorate, and more than twice as high among men compared to women in the Duhok governorate. Higher exposure of the men to the contaminants of military warfare during the last three decades of the conflict in Iraq might play an essential role in the elevated kidney cancer cases. The kidney is considered to be the most susceptible target organ to DU toxicity, relative to other organs 26. Studies have shown that renal cells damaged by DU toxicity can cause kidney cancer 28. Cancer of the kidney is on top six of the most common cancer type worldwide in 2018, with incidence rates about 2.2% of all cancer sites, and the leading cause of death in around 1.8% of cancer cases. Consequently, mortality and incidence rates of kidney cancer among men were approximately double the rates among women 3.
Colorectal cancer was the third most common cancer among women and the fifth among men in Erbil governorate between 2013 and 2019. It represented the fifth most prevalent cancer in the Duhok governorate for both sexes. The reasons for the burden of colorectal cancer in the KRG are believed to reflect the changes in lifestyle and dietary factors, including smoking and obesity, which are associated with Westernized lifestyle factors 29. In 2018, colorectal cancer was the second most prevalent cancer among women worldwide, and the third among men; overall, colorectal cancer ranked third in prevalence, but second worldwide in mortality 3. Likewise, in neighbouring countries such as in Iran, colorectal cancer ranked the third most frequent cancer in 2015 30.
In the Duhok governorate, skin cancer was the fourth most commonly diagnosed cancer among both sexes from 2013 to 2019. In Erbil governorate it was among the top four most commonly diagnosed, and the sixth most frequent cancer among men. Relative to other areas of Iraq, skin cancer cases in the KRG are significantly higher, which can be linked to a geographical location and other lifestyle variables, such as the use of sun blockers, excessive ultraviolet (UV) exposure, sun exposure times, and occupancy 31. In 2015, the Iraqi Cancer Registry (IRC) declared skin cancer as the ninth most frequent cancer in Iraq, and incidence rates among males and females were 3.9% and 2.6%, respectively 2. Globally, in 2018, melanoma skin cancer was the 8th and 9th most common skin cancer in women and men, respectively, in High Development Index (HDI) countries 3.
Prostate cancer ranked as the fourth most common cancer among men between 2013 and 2019 in Erbil governorate, accounting for almost 10% of male cases, whereas in Duhok governorate it was the seventh most frequently diagnosed cancer, accounting for 5% of male cases. Prostate cancer is the second most widely diagnosed cancer in men, with 13.5% among all cancer types worldwide; and the world's fifth-largest cause of cancer death 3. The prostate cancer incidence rate in 2018 was 6.6% in Iraq, which is lower than in most neighbouring countries including Iran (16.6%), Jordan (14.7%), Kuwait (21.6%), Syria (20.1%), and Turkey (41.7%); Saudi Arabia also has 6.6% incidence 32. The variations in incidence rates could be due to differences in the testing method for prostate-specific antigens (PSA) 33.
The overall cancer incidence was higher in Erbil than in Duhok. One of the most important risk factors for cancer incidence is age 34. In this study, the median age (55 years) of cancer patients was similar to the results of other studies conducted in Middle Eastern countries, such as Jordan (55 years 35 and 56 years 36) and Palestine (55 years 37), while cancer patients in the present study were generally about ten years younger than in Western developed countries. The median age of cancer patients in Norway is 69 years 38, and in the US it is 66 years 39. This could be attributable to the Kurdish population and other nations in the Middle East having younger populations than Western countries.
The highest percentages of diagnosed cases reported in this study were in Erbil (23.3%) and Duhok (22.8%) for patients aged between 60–69 years. This result was in line with previous reports finding 23.1% 2 and 19.7% 6, but inconsistent with reports in neighbouring countries, where the age structure of the population is approximately similar, such as in Jordan (23%) 40. However, the highest incidence was found in patients aged 70–79 years in some European countries, like the UK with 28.34% and Norway 27.7% 38.
Paediatric cancers among children (aged 0–14 years) and adolescents (aged 15–19 years) are relatively rare and have a distinct profile, but account for a higher percentage of cancer in developing countries than in developed countries, which is partly due to the younger age structure of developing countries, including Iraq. To the best of our knowledge, this is the first population-based study to estimate ASIR and tumour profile in paediatrics. The average ASIR of cancer in children per 100,000 populations in this study was 11.08 and 8.17 in Erbil and Duhok, respectively. This result is lower than that observed in a previous study during 2012–2016 in Basra 41, and relatively similar to the incidence of some neighbouring countries, such as Iran (11.9) 42, Jordan (11.38) 43, and Saudi Arabia (9.8) 44.
In childhood, the cancer rate accounted for 3.9% and 4.8% of all registered cases in Erbil and Duhok, respectively, with a child proportion of 36%, and the rate was less than the 7.75% reported in the first cancer report in Iraq, with a child proportion of 49% out of the Iraqi population 45. However, the cancer rate is in agreement with the results of the Jordanian child cancer rate of 7.75% 40. However, the rate is much higher than that of some developed countries, where the frequency is less than 1%, such as in Norway and the UK, where frequency was 0.4 and 0.5, respectively 38.
The overall average of ASIR per 100,000 population in adolescents in this study was 38.62 and 27.46 in Erbil and Duhok, respectively, which is higher than rates reported in some developed countries, for example: 19.83 in Portugal, 21.1 in the US, 26.1, in Austria, and 28.2 in Piedmont (Italy), respectively 46–48. The frequency of all new cases in Erbil and Duhok was approximately comparable to the frequency of the Iraqi Cancer Registry from 2018, and was much higher than in Western countries.
Blood cancers were the most common cancer among children and adolescents, and were more prominent among male than female children. This data is in agreement with previous local studies 2,13,41,45 and most other parts of the world 49,50. Currently, the second most common cancer type in Erbil is kidney cancer, followed by lymphoma; in Duhok, it is soft tissues followed by brain cancer. However, this data is not in line with data reported by the Iraqi Cancer Registry (2018), which found cancer of the central nervous system (CNS) to be the second most common type of cancer, followed by lymphoma 49. Among adolescents in the present study, lymphomas and CNS tumours vs lymphomas and soft tissue cancers were the second and third most common cancers in Erbil and Duhok, respectively. In Iraq as a whole, CNS cancers and lymphomas were the second and third most common cancers 2
Finally, breast cancer is rare under the age of 20 years in women 51, and the current study affirmed this, but the small incidence of breast cancer reported among this age group was more aggressive than in older patients 52/ Young age is an independent poor prognostic factor in breast cancer 53. Hence, it is important to take breast cancer screening programs at an earlier age into consideration.
The stages of cancer disease are classified according to the TNM system, which is expressed as 0, I, II, III, and IV 54. Results of previous studies concluded that two-thirds of global cancer deaths occurred in less developed countries as a result of late-stage diagnosis and lack of adequate treatments 55,56. It has been documented that many influencing factors can determine the late-stage diagnosis of cancer, such as inadequate screening tests, education, and cultural awareness 57. Cancer type is another important factor that determines the differences in cancer stages among patients. For example, lung, stomach, colorectal, pancreas, and liver cancer were recorded to be among the highest frequency of late-stage diagnosis compared to other types of cancers in the skin, prostate, uterus, and breast 58,59. However, the results of many Iraqi studies exhibited that the majority of breast cancer cases are detected at very advanced stages 8,57,60,61. Therefore, to minimize the consequence of late diagnosis, persistent monitoring of cancer incidence by stage should be prioritized 62.
In terms of frequency distribution in the KRG between 2013 and 2019, the highest rates were recorded in the centre of Erbil, and the lowest in Mergasor, regarding the cancer risk distribution. In Duhok, the highest and lowest rates were reported respectively in Duhok centre and Berdehresh district. To our knowledge this is mostly due to early detection through mammography screening programs in urban centres. By increasing the social role of women in urban areas, the social effects of exposure to cancer risk factors can be useful in cancer development, so in major cities like Erbil and Duhok it is more prevalent compared to rural and small towns with lower population densities and differing lifestyles 23.
Many limitations may influence the interpretations of cancer incidence trends discussed here. First, the lack of knowledge on cancer mortality burden and death certificates in our study is more likely due to administrative bureaucracy, which affects the accuracy of cancer rates in this area. Second, we define local variations in cancer rates mainly based on only two selected cancer registries (Erbil and Duhok), and missing differences for specific cancer sites in the Sulaymaniyah governorate. Third, the restriction of screening and imaging approaches in cancer detection centres may partly explain the low incidence rates for certain cancers, masking the real disease prevalence.