Incidence rate of thyroid cancer in Iranian population, trend analysis from 2003 to 2009

Document Type: Original Article

Authors

1 Biostatistics Dept., Shahid Beheshti University of Medical Sciences, Tehran, I.R. Iran

2 Gastroenterology and Liver diseases Research Center, Shahid Beheshti University of Medical Sciences, Tehran, I.R. Iran

Abstract

Background and aims: Thyroid cancer is the most common endocrine malignant and papillary cancer and three times more prevalent in women than men. The aim of this study was to evaluate the incidence rate and trend of thyroid cancer in Iranian population. Methods: National incidence was rated by Iran National Cancer Registry data derived from Iran’s annual national cancer registration reported from 2003 to 2009. The crude rate and age standardized rate were used to express the incidence of thyroid cancer. Results: The results indicated that, the incidence of thyroid cancer increased from 2003 to 2009. The age standardized rate for women and men increased from 2.02 and 0.82 to 4.2 and 1.36 per 100,000, respectively. Conclusion: This study indicated remarkable increasing trends in thyroid cancer incidence. So, attention to high risk groups and public programs is necessary to reduce the incidence of this cancer in future.

Keywords

Main Subjects


INTRODUCTION

Cancer is a major cause of morbidity and mortality worldwide and its burden is globally increasing. Although endocrine cancers are relatively uncommon, they may be one the most important and potentially treatable cancers. In fact, thyroid cancer is the most prevalent form of endocrine cancer, accounting for 1% of all new cancers (0.5% of cancers in men and 1.5% of cancers in women).1,3 The worldwide incidence rate of thyroid cancer (TC) is generally lower than 3 per 100,000 in men and 5 per 100,000 in women.4-8 TC is indeed one of 10 (the eighth) leading common cancers among women in the world.9

TC has four main histological types; papillary (PTC) accounts for 80%, follicular (FTC) 10-15%, medullary (MTC) 5-7%, and anaplastic (ATC) 1-2% of all thyroid cancer types. In addition, PTC is the most prevalent type, and it is three times more common in women than men.5,8,10 Five-year survival rate for PTC is higher than 90%, for FTC higher than 90%, for MTC 30-80%, and for ATC 1-17%.11 TC is mostly diagnosed among people aged from 45-54 years with median age of diagnosis of 50 years. The percentage of mortality from TC is highest among people aged 75-84 with median age of 73 years at death.12

In a survey conducted by the Iranian Cancer Institute, 1.8% of all cancers and 76.1% of all endocrine cancers constituted by the neoplasm of thyroid gland; for example, in a study in Iran, mean age of Iranian patients was 42.8 years (95% CI: 41.9-43.7) with markedly older male patients.8,13 Also, the female to male ratio was about 1.8, while this ratio was 1.3 for anaplastic carcinoma due to the higher proportion of the affected men.8,14 The aim of this study was to determine the trends of TC incidence in Iranian general population from 2003 to 2009.

METHODS

The data were extracted from Iran National Cancer Registry data derived from Iran’s annual national cancer registration reported from 2003 to 2009 (Islamic Republic of Iran Ministry of Health and Medical Education, Center for Disease Control and Prevention, Noncommunicable Deputy Cancer Office, 2009).15 The Iran Ministry of Health and Medical Education registers all the new cancer cases, according to pathology reports, in all provinces and the data are publicized after revision.

Age standardized rate (ASR) and crude death rate (CDR) of TC (ICD-9: 193) for men and women from 2003 to 2009 were expressed per 100,000 as the annual incidence, overall and for all provinces. Then, the trend of ASR, CDR, and five most common morphologies of TC in Iran were drawn.

RESULTS

All incidence records of TC from 2003 to 2009 were included in the analysis. The ASR of TC dramatically increased during these years from 1.42 to 2.78 per 100,000 for both men and women. In women, this rate varied from 2.02 to 4.2 per 100,000 and in men from 0.82 to 1.36 per 100,000. The CDR of TC increased from 1.24 to 2.57 per 100,000 for both men and women. In women, it varied from 1.75 to 3.96 per 100,000 and in men from 0.74 to 1.17 per 100,000 (Table 1 and Figure 1). The highest ASR of TC was derived in Isfahan province for all years under study. For some provinces, no data reported (Table 2).

 Table 1: Crude Rate and ASR (per 100,000) for thyroid cancer incidence in Iran

Years

ASR

Crude Rate

females

males

females

males

2003

2.02

0.82

1.75

0.74

2004

2.8

1.06

2.42

0.9

2005

3.47

1.16

2.93

0.98

2006

3.76

1.3

3.32

1.12

2007

3.4

1.11

2.98

0.95

2008

4.47

1.51

3.85

1.31

2009

4.2

1.36

3.96

1.17

 

Figure 1: ASR and CR of thyroid cancer for female and male in Iran (2003-2009)

 

Table 2: The ASR for thyroid cancer incidence (per 100,000) from all provinces in Iran

Province

2004

2005

2006

2007

2008

ASR F

ASR M

ASR total

ASR F

ASR M

ASR total

ASR F

ASR M

ASR total

ASR F

ASR M

ASR total

ASR F

ASR M

ASR total

East Azarbaijan

2.89

1.24

2.065

1.14

0.4

0.77

0.35

0.48

0.415

4.46

1.67

3.065

7.09

2.44

4.765

West Azarbaijan

1.47

0.43

0.95

1.5

0.45

0.975

3.21

0.84

2.025

2.82

1.34

2.08

2.74

1.2

1.97

Ardebil

4.25

0.95

2.6

0.27

0.19

0.23

3.76

1.3

2.53

2.49

0.2

1.345

3.03

1.8

2.415

Esfahan

4.01

2.09

3.05

5.48

1.3

3.39

5.85

1.54

3.695

5.62

1.48

3.55

8.17

2

5.085

Ilam

3.28

2.2

2.74

1.03

   

2.2

0.84

1.52

0.24

0.89

0.565

2.38

0.66

1.52

Bushehr

1.36

0.67

1.015

2.18

2.02

2.1

2.21

0.83

1.52

3.36

0.63

1.995

2.93

0.62

1.775

Tehran

2.76

0.64

1.7

3.57

1.14

2.355

3.59

1.22

2.405

2.8

0.93

1.865

5.29

1.74

3.515

Chaharmahalbakhtiari

2.93

2.89

2.91

8.19

1.8

4.995

7.99

1.02

4.505

5.12

0.78

2.95

5.52

2.53

4.025

South Khorasan

     

0.86

0.32

0.59

0.37

0.43

0.4

0.76

   

2.08

1.52

1.8

KhorasanRazavi

1.98

1.24

1.61

1.9

0.78

1.34

3.66

1.19

2.425

2.43

0.86

1.645

3.01

0.99

2

North Khorasan

     

1.97

0.74

1.355

0.69

0.33

0.51

1.45

0.56

1.005

2.11

2.56

2.335

Khozestan

2.47

1.06

1.765

2.08

0.47

1.275

2.84

0.56

1.7

1.99

0.64

1.315

4.1

0.87

2.485

Zanjan

1.85

0.67

1.26

2.71

0.17

1.44

2.23

0.9

1.565

1.78

0.56

1.17

2.11

0.43

1.27

Semnan

2.34

1.53

1.935

1.7

1.13

1.415

3.9

1.15

2.525

1.2

0.97

1.085

1.68

0.64

1.16

Sistanbalochestan

1.25

0.32

0.785

0.79

1.03

0.91

1.26

0.57

0.915

0.88

0.64

0.76

1.53

0.72

1.125

Fars

2.2

0.82

1.51

3.54

1.3

2.42

3.34

1.36

2.35

5.61

1.59

3.6

6.25

1.87

4.06

Ghazvin

4.04

0.62

2.33

3.83

1

2.415

3.9

0.97

2.435

3.51

1.05

2.28

2.92

1.56

2.24

Qom

1.63

1.28

1.455

2.37

0.35

1.36

2.74

0.93

1.835

2.9

0.47

1.685

1.18

0.48

0.83

Kordestan

1.61

0.33

0.97

1.18

0.36

0.77

2.16

0.59

1.375

2.16

1.06

1.61

2.71

1.22

1.965

Kerman

2.89

2.16

2.525

3.28

0.37

1.825

3.61

1.15

2.38

3.77

1.47

2.62

4.61

1.1

2.855

Kermanshah

1.42

1.05

1.235

2.83

1.36

2.095

3.44

0.43

1.935

3.05

1.46

2.255

4.26

1.46

2.86

Kohgiloyeboyerahmad

4.76

1.24

3

1.39

1.25

1.32

1.86

1.61

1.735

5.85

0.36

3.105

4.39

0.93

2.66

Golestan

2.65

0.75

1.7

1.78

0.64

1.21

3.42

1.36

2.39

2.26

0.51

1.385

2.93

1.41

2.17

Gilan

1.99

0.54

1.265

2.29

0.67

1.48

2.49

1.2

1.845

1.72

1.33

1.525

5.77

1.61

3.69

Lorestan

1.91

0.35

1.13

1.63

0.28

0.955

2.32

1.31

1.815

2.28

0.81

1.545

2.82

1.95

2.385

Mazandaran

2.8

0.78

1.79

3.28

1.33

2.305

4.3

0.85

2.575

3.51

0.86

2.185

3.9

1.69

2.795

Markazi

1.46

0.66

1.06

3.42

0.36

1.89

3.78

1.28

2.53

2.5

0.63

1.565

     

Hormozgan

2.04

0.19

1.115

1.66

0.55

1.105

1.47

0.45

0.96

1.58

0.13

0.855

     

Hamedan

1.95

0.89

1.42

3.02

0.6

1.81

3.2

1.47

2.335

1.92

0.62

1.27

     

Yazd

5.01

0.22

2.615

4.26

0.99

2.625

3.62

2.38

3

4.63

0.9

2.765

     

M: Male, F: Female

The trend of five most common morphologies of TC in Iran from 2003 to 2008 was also assessed; the papillary adenocarcinoma was the most common thyroid tumor followed by papillary carcinoma follicular variant, follicular adenocarcinoma, medullary carcinoma, and anaplastic carcinoma (Table 3).

Table 3: The number of cases according to five most common morphologies of thyroid cancer in Iran

Years

a

b

c

d

e

F

M

Both

F

M

Both

F

M

Both

F

M

Both

F

M

Both

2003

414

180

594

50

18

68

47

12

59

27

23

50

9

8

17

2004

568

204

772

78

22

100

44

21

65

25

26

51

16

7

23

2005

695

260

956

78

19

97

64

16

80

48

30

78

16

9

25

2006

824

270

1094

91

25

116

55

14

69

43

29

72

18

10

28

2007

757

233

990

112

32

144

13

4

17

38

27

65

11

14

25

2008

960

322

1282

90

21

111

66

11

77

48

43

91

14

9

23

a) Papillary Adenocarcinoma, NOS; b) Papillary Carcinoma, Follicular Variant; c) Follicular Adenocarcinoma; d) Medullary Carcinoma, NOS; e) Carcinoma, Anaplastic, NOS.

 

Estimated TC incidence, mortality, and 5-year prevalence, based on GLOBOCAN2012, for the whole world, more developed regions, less developed regions, ASIA, Islamic Republic of Iran, WHO Americas region (PAHO), and WHO Europe region (EURO), are presented in Table 4.

Table 4: Estimated thyroid cancer incidence, mortality, and 5-year prevalence according to GLOBOCAN2012

Varieties

gender

Incidence

Mortality

5-year prevalence

Number

%

ASR (W)

Number

%

ASR (W)

Number

%

Prop.

World

Men

68179

0.9

1.9

12627

0.3

0.3

271270

1.8

10.4

Women

229923

3.5

6.1

27142

0.8

0.6

934805

5.6

36.0

Both sexes

298102

2.1

4.0

39769

0.5

0.5

1206075

3.7

23.2

More Developed Regions

Men

29672

0.9

3.6

3651

0.2

0.3

121600

1.4

24.3

Women

93104

3.3

11.1

6740

0.5

0.4

392196

4.7

72.7

Both sexes

122776

2.0

7.4

10391

0.4

0.4

513796

3.0

49.4

Less Developed Regions

Men

38507

0.9

1.4

8976

0.3

0.4

149670

2.2

7.1

Women

136819

3.6

4.7

20402

0.9

0.7

542609

6.1

26.4

Both sexes

175326

2.2

3.0

29378

0.6

0.6

692279

4.4

16.7

ASIA

Men

32858

0.9

1.5

7127

0.3

0.3

129384

2.1

0.8

Women

111621

3.6

5.0

15286

0.8

0.7

451739

6.3

28.9

Both sexes

144479

2.1

3.2

22413

0.5

0.5

581123

4.4

18.3

Islamic Republic of Iran

Men

513

1.1

1.4

181

0.6

0.5

1885

2.4

6.4

Women

1512

3.8

4.0

429

1.8

1.4

5772

6.4

20.0

Both sexes

2025

2.4

2.7

610

1.1

0.9

7657

4.5

13.1

WHO Americas Region (PAHO)

Men

19401

1.3

3.7

1879

0.3

0.3

81176

2.1

23.0

Women

66065

4.6

12.1

3372

0.5

0.5

280246

6.8

76.0

Both sexes

85466

3.0

8.0

5251

0.4

0.4

361422

4.5

50.1

WHO Europe Region (EURO)

Men

14036

0.7

2.5

2379

0.2

0.3

54900

1.1

15.4

Women

48775

2.8

8.1

5088

0.6

0.5

192534

3.9

49.5

Both sexes

62811

1.7

5.4

7467

0.4

0.4

247434

2.5

33.2

 

DISCUSSION

This study, indicated a remarkable increasing trend in TC incidence, based on the national registry data from 2003 to 2009. This trend was different for men and women. Enhanced detection could contribute to the increased TC incidence in the past decades, but cannot fully explain the increase, suggesting that maybe a true increase exists.16 In addition, when the main reason is the increasing detection, the improvement in small and early-stage tumors should be accompanied by a progressive decline of larger and more advanced tumors. The TC increases, while most prominent for small tumors and across all tumor sizes and stages, suggesting that increasing of detection is not the only reason.17-19 The remarkable increase in incidence of TC in advanced stages, usually clinically apparent, is too difficult to be explained by increased detection. Moreover, the TC increase has been almost exclusively observed for papillary tumors, while improved detection must affect all histotypes.17 Finally, when increasing of detection is the only reason, it is expected that the cancer increase to be observed in all age and gender categories. Indeed, the age-adjusted incidence rates of TC have increased in women more than in men (158% vs. 106%) with a clear birth cohort pattern, possibly reflecting changes in risk factors and the birth cohort contribution which suggest that the increasing of detection is not the only reason of the increased incidence of TC.17, 20

Furthermore, by the report of GLOBOCAN 2012, annually 298102 new cases of TC occurred around the world.9 In the United States, TC is the ninth leading cancer and it is estimated that new cases would register 62,980 in 2014. Five-year survival was about 97.8% in 2004-2010. Using statistical models of analysis, rates of new TC cases have been rising on average by 5.5% per year over the last 10 years.12 In the United Kingdom 2,727 people were diagnosed with TC in 2011. Around 75.0% of adult TC patients (74.2% of men and 78.9% of women) in England and Wales survived five years or longer during 1996-1999.21 TC represents 2.1% of all new cancer cases in the world, 3.0% in WHO Americas region, 2.4% in Iran, 2.2% in less developed regions, 2.1% in Asia, 2% in more developed regions, and 1.7% in WHO Europe region.9

Study of potential etiologic and risk factors of TC showed that radiation exposure, genetic factors, pre-existing thyroid disease, hormonal and reproductive factors (as the cancer is more frequent in women),  and dietary factors (specially iodine) could play the  main roles in pathogenesis of TC.22,23

The limitation of this study was the incomplete data which were collected from all provinces before 2004 and no published information for provinces after 2008. In addition, from 2003 to 2009, the coverage of registered new cancer cases was increasing. So, for the early years under the study, the collected data could suffer from underestimation.

CONCLUSION

This study indicated an increasing incidence of TC in Iranian population. Since many cases of TC could be treated successfully, it is expected to diagnose TC at early stages. Therefore, the development of a guideline can be helpful to diagnose TC at early stages. Moreover, attention to high risk groups and setting awareness programs should be focused to reduce the incidence of this cancer in the future.

ACKNOWLEDGMENT

We gratefully thank all workers assisted us in conducting this research.

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