Leukemia Epidemiology in Karbala province of Iraq

Objective: Investigate epidemiology of leukemia in Karbala province of Iraq, compare and identify possible changes with other populations.

Methods: This was retrospective descriptive study for more than 400 leukemia patients in Karbala province from November 2011 to May 2018with evaluation of age, gender distribution, types distribution , and frequency distribution types of leukemia according to age and gender.

Result: About 402 patients with leukemia were retrospectively enrolled in this study at the median age of 30 years. Males accounted for a higher proportion of leukemia patients, 58.2 % compared to 41.8% females, with a male to female ratio of nearly 1.4:1. Acute lymphoblastic leukemia (ALL) was the most prevalent in the study group, contributing 41% (median age 10 years), followed by chronic myeloid leukemia (CML) 24.1% (median age 42 years), acute myeloid leukemia (AML) 19.2% (median age 36 years) and chronic lymphocytic leukemia(CLL) of less frequent type which contributed only 15.7% (median age 60 years).

Conclusion: This is the first statistical study of leukemia in Karbala. It can be used as basic information to investigate epidemiological characteristics, to evaluate progress in recent years and to develop future leukemia strategies. More statistical leukemia analyses in Iraq are needed.

 Introduction

In 2012, there were about 352,000 new cases of leukemia (2.5 percent of all new cancer cases) and 265,000 deaths (3.2 percent of all cases). The lowest incidence rates in Middle and West Africa (less than 3 per 100,000 males and less than 2 per 100,000 females) and the highest in North America and Australia / New Zealand (more than 10 per 100,000 males and 7 per 100,000 females).Sub Saharan Africa's estimated low incidence rates may be due to a failure to diagnose the disease in old or very young patients [1].

In Iraq, leukemia represents the fourth common cancer in both male and female. In 2009 Iraqi Cancer Board recorded 13951 cases of leukemia in Iraq in the years from 1991 to 2009 representing 6.59% of new cases [2]. In Karbala province which is a town in central Iraq, about 100 km southwest of Baghdad (Figure 1) [3], and has an estimated population of 1013254 people in 2009 , leukemia was the sixth common cancer with incidence rate 3.26 /100000Population [2].

Leukemia is usually had four main categories, with different presentations and outcomes: acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, and chronic myeloid leukemia. Males have a slightly higher incidence of leukemia than females. Leukemia rates also vary geographically and ethnically. In the US, the Caucasian incidence is higher than in African - Americans and Hispanics. The lowest rate of incidence among Americans / Alaskans [4].

Ionizing radiation exposure, chemicals like benzene, pesticides, chemotherapy, smoking cigarettes, viral infection and genetic disorders are recognized as leukemia risk factors [5][6][7][8][9][10][11]. However, these risk factors can only explain minority cases and the etiology of leukemia remains largely unknown [12].

In this study, we investigated leukemia distribution among the population in Karbala province of Iraq from 2011 to 2018. It can help to provide basic information to investigate epidemiological characteristics, to assess progress in recent years and to develop future leukemia treatment strategies.

Materials and Methods

We conducted a retrospective, descriptive, epidemiological study of leukemia patients in the Karbala province, diagnosed between November 2011 and May 2018. The data for this study were obtained from the cancer registry department in Al Hussein Cancer Centre in Karbala, which was established in November 2011and there were no accurate leukemia data available before. This Centre covers Karbala population and most of children and adults with leukemia were referred to this center for treatment. It is presently the only available source of information and most of the patients with leukemia attended the center were enrolled in this study. Data provided information about the gender of patients, diagnosis and the years of diagnoses.

Diagnoses were made on peripheral blood films and morphology of bone marrow including cytochemical staining and immunophenotyping. Patient with the non-conclusive result was excluded from this study. The selected topic was accepted by the scientific committee; official acceptance was taken from health authorities to conduct this study. Collected information was kept confidential.

Statistical analysis

The statistical package for social sciences (SPSS) for Windows, version 24 was used for entering, managing and analysis of data. Descriptive statistics presented as count (frequency), proportions, median and interquartile range (IQR), findings presented in tables and figure using MS-office software version 2013.

Results

A total of 402 patients diagnosed with leukemia were retrospectively analyzed during our study. Patients ages were between 1 year and 90 years, 234 were males (58.2%) and 168 were females (41.8%), with an M/F ratio of 1.4:1. Among all leukemia cases, 22.6% (n = 91) were below 10 years. The median age of diagnosis was 30 years for all cases (Table 1).

Variable Count %
Age (year ≤ 10 91 22.6%
11 – 20 72 17.9%
21 – 30 43 10.7%
31 – 40 43 10.7%
41 – 50 44 10.9%
51 – 60 42 10.4%
61 – 70 47 11.7%
> 70 20 5.0%
Median (IQR*) 30 (12 – 54) -
Gender Male 234 58.2%
Female 168 41.8%

*IQR: Interquartile range

Regarding the distribution of types of leukemia, ALL was the more prevalent type among the studied group, contributed (41%, median age 10 years), followed by CML (24.1%, median age 42), AML (19.2 %, median age 36 years) and the less frequent type was CLL which contributed only (15.7% ,median age 60 years) [Figure 2 &Table 2].

Leukemia types Number of cases Distribution(%) Median age(year)
ALL 165 41% 10
CLL 63 15.7% 60
AML 77 19.2% 36
CML 97 24.1% 42
Total 402 100 30

The distribution of types of leukemia according to age group revealed that ALL was the more prevalent type of leukemia among the younger age groups it was found in 87.9% of leukemia cases in the age ≤ 10 years.AML was more prevalent in the age groups 31 – 40 years, and 61 – 70 years where it was found in 32.6% and 31.9% of cases in these two age groups, respectively.

CLL was more prevalent among those aged more than 50 years old with 45% of leukemia cases. Interestingly, none of the cases at the age of 30 years or below had CLL. For the CML was prevalence among those 41-50 years presenting 50% while representing only 2% of leukemia in patients below 10 years old (Table 3).

Total

Cases

 Type of leukemia
ALL AML CLL CML
Age (year) Count % Count % Count % Count %
≤ 10 91 80 87.9 9 9.9 0 0.0 2 2.2
11 – 20 72 50 69.4 15 20.8 0 0.0 7 9.7
21 – 30 43 19 44.2 7 16.3 0 0.0 17 39.5
31 – 40 43 7 16.3 14 32.6 3 7.0 19 44.2
41 – 50 44 4 9.1 8 18.2 10 22.7 22 50.0
51 – 60 42 3 7.1 5 11.9 21 50.0 13 31.0
61 – 70 47 1 2.1 15 31.9 19 40.4 12 25.5
> 70 20 1 5.0 4 20.0 10 50.0 5 25.0
Gender  
Male 234 101 43.2 42 17.9 39 16.7 52 22.2
Female 168 64 38.1 35 20.8 24 14.3 45 26.8

Discussion

The quality and ability to access to the health systems can explain the geographical differences in leukemia, although etiological factors including gene-environment interactions would probably play a role. Global leukemia rates in males were generally higher than females with a total M/F of 1:4, which was the same as in our study [13].

In our study ALL was the more prevalent type among the studied group; contributed 41%, followed by CML 24.1%, AML 19.2%, and the less frequent type was CLL which contributed only 15.7%. In a study done in Sulaymaniyah province of Iraq, ALL was the most common type of leukemia with 44% in all cases, CML was the second type with 20% of cases followed by CLL, 18% and AML, 17% [14].

In Croatia, the most common type of leukemia was CLL, which accounted for 42% of leukemia, followed by AML with 27%, ALL with 17% and CML with 14% [15].In Bangladesh, on the other hand, AML was the most prevalent hematological malignancy 28.3% followed by CML 18.2 %, ALL 14.1 % and CLL 3.7 % was the least common [16].

In Karbala ALL was the more prevalent type of leukemia among the younger age groups of 30 years or below; it was found in 87.9% of leukemia cases in the age ≤ 10 years with a median age of 10 years. This is close to the study done by (Elew et al., 2009) in Baghdad that showed ALL represent 90.5 % of leukemia cases below 10 years old [17]. This result was also closed to data in the United States with a median age of only 15 years and about 60% of patients were under 20 years of age. Although in India, about 60 to 85% of all reported leukemia was ALL [18][19].

Incidence of AML in North America, Oceania, and Europe is relatively common, whereas adults AML in Latin America and Asia is uncommon. AML affects older people with a median age at present in Western countries around 65 years [4][20]. While in our study median age was only 36 years old that closer to the previous study in Baghdad with ~33years and studies in Bangladesh with~ 35 years and India with ~30 years [16][21][22].

The median age of CML in Karbala was 42 years, which is older than the previous study done in Iraq with a median age of ~ 37 years. Our result was closer to the median age in Turkey 46 years and Bangladesh was 40 years old. Interestingly much younger than of US with a median age of 65years and Europe 55 years old [16][23][24][25][26][27].

CLL is a rare hematological disorder in Asia, although it represents the most common leukemia in the West that affects elderly people. In the US, for example, CLL accounts for about ~34% of leukemia cases [4][28].

CLL median age in Karbala was 60 years old and none of the cases at the age of 30 years or below, this close to previous studies in Iraq with median age ~60 years [29]. Our result also was closer to the median age in Turkey with 63years, India median age with ~60years and Bangladesh 60 years old [16][30][31][32].

While our study median age was younger than that in the USA, Europe, and Australia which is approximately 70 years of age [32][33][34].

In conclusion the distribution of leukemia in Karbala differs from other countries, with younger median age than western countries. This may be explained by the fact that > 58% of the population under 25 years old and about 3.4% of the population above 65 years [35]. More studies are needed to understand the leukemia patterns and dissemination in Iraq and recognize biology, genetics & possible risk factor in Iraqi patients.

Acknowledgements

We would like to thank Mrs.Afnan Al Wakeel and Mr. Hekmat Hamada Baqir from Karbala Cancer Registry Center, without their help this study couldn’t see the light of day.

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