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BREAST - ORIGINAL ARTICLE
Year : 2011  |  Volume : 48  |  Issue : 4  |  Page : 406-409
 

Age pattern of the occurrence of breast cancer in the northwest of Iran


1 Department of Medicine, Hematology and Oncology Research Center, Tabriz, Iran
2 Department of Medicine, Hematology and Oncology Research Center; Department of Community and Family Medicine, National Public Health Management Center, Tabriz, Iran
3 Department of Medicine, Hematology and Oncology Research Center; Department of Epidemiology and Biostatistics, Tabriz University of Medical Sciences, Tabriz, Iran

Date of Web Publication25-Jan-2012

Correspondence Address:
S Dastgiri
Department of Medicine, Hematology and Oncology Research Center; Department of Community and Family Medicine, National Public Health Management Center, Tabriz
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-509X.92256

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 » Abstract 

Breast cancer represents 27% of the cancers and 19% of the cancer deaths in female population. The aim of this study was to document the age pattern of the incidence of breast cancer in Iranian female population in the northwest region of the country. The study subjects were 1764 patients with breast cancer diagnosed/registered in the six university clinics between 1988 and 2008 in the northwest of Iran. The highest occurrence rates were observed for the birth year cohorts 1940-1949 (for 59-69 years old), 1950-1959 (for 49-58 years old), and 1960-1969 (for 39-48 years old). Among these three cohorts, the highest rate was observed in 1950-1959 birth year cohort (284.38 per 100,000 female populations, 95% CI: 260-310). This rate was significantly higher compared with the similar rates of other birth cohorts. There was no statistically significant difference between various years in terms of the average age at the diagnosis of breast cancer in our study setting. Despite the previous research reports, we found no significant difference between the mean ages at diagnosis of breast cancer from 1988 to 2008 in Iranian female population.


Keywords: Age pattern, breast cancer, incidence


How to cite this article:
Eivazi-Ziaei J, Dastgiri S, Kermani I A, Nikanfar A, Esfahani A, Sanaat Z, Sadeghi-Bazargani H, Vaez J. Age pattern of the occurrence of breast cancer in the northwest of Iran. Indian J Cancer 2011;48:406-9

How to cite this URL:
Eivazi-Ziaei J, Dastgiri S, Kermani I A, Nikanfar A, Esfahani A, Sanaat Z, Sadeghi-Bazargani H, Vaez J. Age pattern of the occurrence of breast cancer in the northwest of Iran. Indian J Cancer [serial online] 2011 [cited 2019 Dec 7];48:406-9. Available from: http://www.indianjcancer.com/text.asp?2011/48/4/406/92256



 » Introduction Top


The highest occurrence of breast cancer occurs after age 35, with 83% of the cases occurring after age 50 with only 1.5% under age 30. [1] However, some Asian countries (i.e., Iran, India, Korea, southeast Asian region, and Arab world) are experiencing a different age pattern of disease (usually younger) at diagnosis compared with the patients in western developed countries. [2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12],[13],[14],[15] The proportions of young patients (i.e., 35 years or less) vary from about 10% in developed countries to 25% in some Asian countries indicating a poorer prognosis in the region. [10]

Yoo et al, [16] from Korea, reported an inverted V-shaped curve observed in some Asian countries, while the similar curve in western developed countries was almost linear increasing by age.

The aim of this study was to document the age pattern of the incidence of breast cancer in Iranian female population in the northwest region of the country.


 » Materials and Methods Top


This study was carried out in Tabriz Hematology-Oncology research center of the Tabriz University of Medical Sciences in the northwest of Iran. The study subjects were 1764 patients diagnosed/registered in the six university clinics between 1988 and 2008. In early years full data were not available because of the problems in registration system, while in latter years full data were recorded. Total female population of the area was obtained from the regional and national Bureau for Vital Statistics.

Descriptive statistics, survival model, and occurrence of breast cancer by birth year were calculated for the study population. Ninety-five percent confidence intervals (95% CI) were calculated to assess the statistical significance of the data.


 » Results Top


Occurrence of breast cancer (per 100,000 female populations) by birth year cohorts in three different age groups (2-40, 41-60, and 61+ years) was investigated in this study. The highest rates were observed for the birth year cohorts 1940-1949 (for 59-69 years old), 1950-1959 (for 49-58 years old), and 1960-1969 (for 39-48 years old). Among these three cohorts, the highest rate was observed in 1950-1959 birth year cohorts (284.38 per 100,000 female populations, 95% CI: 260-310). This rate was significantly higher compared with the similar rates of other birth cohorts. [Table 1] shows the occurrence of breast cancer by birth years.
Table 1: Occurrence of breast cancer by birth year (per 100,000)

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[Table 2] and [Figure 1] show the mean age at the diagnosis of breast cancer subjects. There was no statistically significant difference between various years in terms of the average age at the diagnosis of breast cancer in our study setting.
Figure 1: Mean age at diagnosis

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Table 2: Mean age at diagnosis of breast cancer

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 » Discussion Top


In this study, the age pattern of the incidence of breast cancer in Iranian female population in the northwest region of country was investigated. No significant difference was found between the mean ages at diagnosis of breast cancer from 1988 to 2008. Occurrence of breast cancer by birth year cohorts in three different age groups was statistically significant.

The role of some risk factors for breast cancer has been investigated in the country in the recent years. Ebrahimi et al[17] have shown that family history and marital status may have an impact on the incidence of breast cancer in Iranian women. A multivariate analysis in the northern Iran showed that higher education, late menopause, history of induced abortion, first-degree family history of the disease, and body mass index were all possible risk factors for the occurrence of breast cancer. Furthermore, having more episodes of full-term pregnancy, longer duration of breast feeding, and parity of two or more were shown to be protective factors for breast cancer. [18] Known risk factors of breast cancer may, however, vary slightly in different parts of the world. This may indicate that environmental factors might be of greater importance than genetic factors. [17]

In Iran, breast cancer affects women at least one decade younger than their counterparts in the western developed countries. [14] A multicenter research study on Iranian female population showed that the mean age of women with breast cancer was 48.8 years. The highest frequency of breast cancer was observed in the 40-49 age groups (31.8%), while 23% of the occurrence of disease was observed in women younger than 40 years. [14] Some other researches have reported similar findings in other parts of Iran and some Asian countries. [2],[3],[4],[5],[6],[7],[8],[19] Our study on a cohort of Iranian female population in the northwest region of the country, however, showed that the mean age of breast cancer has not considerably changed over the past two decades indicating that there might have not been considerable change in environmental factors over the same time period in the area.

Comparing the mean age at diagnosis for breast cancer can lead to a biased conclusion in different ways:

  • Narrower time span of available information for cancer cases (1988-2008) compared with the wider time span for studying birth cohorts introduces two sources of bias in comparing mean age at diagnosis for different birth cohorts. The first is that those of earlier birth years have lower chance to be diagnosed at younger ages. If we consider a hypothesis that later cohorts are more likely to develop cancer at younger than 39 years of age, the probability of being caught by our registry will even be zero for one-third of the study population. The three first cohorts as 1920-1940 will have a zero probability and there will be an increasing probability trend for the later cohorts which will lead to a biased conclusion that cancer age is going to be decreased through the recent decades. Second, those of later birth years will have lower chance to be diagnosed at older ages and similarly the probability of being caught by our registry at later ages will be zero for a noticeable part of the study population. However, both of these biases are in the same direction; underestimating means diagnosis age for later birth cohorts.
  • Those belonging to the later birth years may differ in medical care seeking behavior from the older ones due to some reasons such as ageism and lower literacy.
  • Due to the slow progression behavior in breast cancer, even without considering the time span limitation in this study, the higher quality of diagnostic facilities in recent decades as well as improved public knowledge and implementation of screening programs in some countries may lead to reporting lower mean ages at diagnosis in recent decades just because of earlier detection of cases. It is, however, clear that although the screening programs in developing countries (including Iran) are not well planned and developed, the awareness of female population of breast cancer and its examination might have lead to an early age of diagnosis in the area.


In conclusion, we found no significant difference between the mean ages at diagnosis of breast cancer from 1988 to 2008 in our female cohort group indicating that breast cancer does not occur earlier in the study population. This is in contrast to what were previously reported from other studies in Iran and some other Asian countries. [2],[3],[4],[5],[6],[7],[8],[15],[19] Despite clinical follow-up of a relatively large birth cohort of breast cancer patients in this study, we cannot rule out the underlying role of underestimation in our findings. More studies are needed to investigate this.

 
 » References Top

1.Marchant DJ. Epidemiology of breast cancer. Clin Obstet Gynecol 1982;25:387-92.   Back to cited text no. 1
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2.Shin HR, Boniol M, Joubert C, Hery C, Haukka J, Autier P, et al. Secular trends in breast cancer mortality in five East Asian populations: Hong Kong, Japan, Korea, Singapore and Taiwan. Cancer Sci 2010;101:1241-6.  Back to cited text no. 2
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3.Long N, Moore MA, Chen W, Gao CM, Lai MS, Mizoue T, et al. Cancer epidemiology and control in north-East Asia - past, present and future. Asian Pac J Cancer Prev 2010;2:107-48.  Back to cited text no. 3
    
4.Moore MA, Manan AA, Chow KY, Cornain SF, Devi CR, Triningsih FX, et al. Cancer epidemiology and control in peninsular and island South-East Asia - past, present and future. Asian Pac J Cancer Prev 2010;2:81-98.  Back to cited text no. 4
    
5.Moore MA, Attasara P, Khuhaprema T, Le TN, Nguyen TH, Raingsey PP, et al. Cancer epidemiology in mainland South-East Asia - past, present and future. Asian Pac J Cancer Prev 2010;2:67-80.  Back to cited text no. 5
    
6.Salim EI, Moore MA, Bener A, Habib OS, Seif-Eldin IA, Sobue T. Cancer epidemiology in South-West Asia - past, present and future. Asian Pac J Cancer Prev 2010;2:33-48.  Back to cited text no. 6
    
7.Salim EI, Moore MA, Al-Lawati JA, Al-Sayyad J, Bazawir A, Bener A, et al. Cancer epidemiology and control in the arab world - past, present and future. Asian Pac J Cancer Prev 2009;10:3-16.  Back to cited text no. 7
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8.Yang BH, Parkin DM, Cai L, Zhang ZF. Cancer burden and trends in the Asian Pacific Rim region. Asian Pac J Cancer Prev 2004;5:96-117.  Back to cited text no. 8
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9.Shin HR, Boniol M, Joubert C, Hery C, Haukka J, Autier P, et al. Secular trends in breast cancer mortality in five East Asian populations: Hong Kong, Japan, Korea, Singapore and Taiwan. Cancer Sci 2010;101:1241-6.  Back to cited text no. 9
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10.Agarwal G, Pradeep PV, Aggarwal V, Yip CH, Cheung PS. Spectrum of breast cancer in Asian women. World J Surg 2007;31:1031-40.  Back to cited text no. 10
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11.Omar S, Khaled H, Gaafar R, Zekry AR, Eissa S, el-Khatib O. Breast cancer in Egypt: A review of disease presentationand detection strategies. East Mediterr Health J 2003;9:448-63.  Back to cited text no. 11
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12.El Saghir NS, Khalil MK, Eid T, El Kinge AR, Charafeddine M, Geara F, et al. Trends in epidemiology and management of breast cancer in developing Arab countries: A literature and registry analysis. Int J Surg 2007;5:225-33.  Back to cited text no. 12
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13.Nokiani FA, Akbari H, Madani H, Izadi B. Prevalence of Breast Cancer in Breast Sample Reports in Iran, 2001-2004. Breast J 2007;13:536.   Back to cited text no. 13
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17.Ebrahimi M, Vahdaninia M, Montazeri A. Risk factors for breast cancer in Iran: A case-control study. Breast Cancer Res 2002;4:R10.  Back to cited text no. 17
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18.Naieni KH, Ardalan A, Mahmoodi M, Motevalian A, Yahyapoor Y, Yazdizadeh B. Risk factors of breast cancer in north of Iran: A case-control in Mazandaran Province. Asian Pac J Cancer Prev 2007;8:395-8.  Back to cited text no. 18
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    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2]

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