Background
Breast cancer in Vietnam
Vietnam, a developing Southeast Asian nation with a population of 91 million, has 84% of its residents belonging to the Kinh ethnicity Breast cancer is the most commonly diagnosed cancer among Vietnamese women, accounting for 32% of new cancer cases and 6% of cancer-related deaths Although the age-standardized incidence rate of breast cancer in Vietnam is 23 per 100,000 women—three to four times lower than in Western countries—this rate has nearly doubled over the past decade Additionally, the peak age for breast cancer patients in Vietnam is 45-55 years, significantly younger than the 65-69 years observed in Western populations.
Breast cancer incidence rates in Vietnam show significant regional variation, particularly between Ha Noi and Ho Chi Minh City, the country's major economic and healthcare hubs Despite both cities having similar ethnic compositions, with over 90% Kinh population, the southern region has experienced a more rapid increase in breast cancer cases In the 1990s, Ha Noi reported the highest incidence rate at 26.7 per 100,000 women, more than double that of Ho Chi Minh City at 12.2 per 100,000 women However, by the following decade, the rate of new cases surged in the south to 19.4 per 100,000 women, while the north saw a slower increase to 29.7 per 100,000 women The reasons behind these disparities in breast cancer rates remain unclear.
Breast anatomy and development
The female breast is a specialized organ located over the pectoralis muscles, primarily responsible for milk production during lactation Its structure comprises three main layers: fatty tissue, connective tissue (stroma), and glandular tissue (epithelium) The breast size is largely determined by the amount of fatty tissue, while the glandular tissue contains 15 to 20 lobes, each with smaller lobules where milk is produced Milk travels through a network of ducts that converge into larger ducts, eventually exiting through the nipple, surrounded by the areola Most breast cancers originate from the cells in the lobules and terminal ducts, which are interspersed within fibrous and adipose tissues that form the breast's mass Additionally, supportive connective tissue and ligaments shape the breast, while nerves provide sensation, and the breast also contains blood vessels, lymph vessels, and lymph nodes.
(Image was created by Patrick J Lynch Reprinted from Wikimedia Commons under the license of Creative Commons)
From birth, a female infant's nipples and milk-duct system begin to form, but significant breast development occurs during puberty when estrogen from the ovaries promotes fat accumulation in connective tissue, leading to breast enlargement As ovulation and menstruation commence, mammary glands develop at the end of the milk ducts, and the breasts continue to mature through menstruation, pregnancy, and breastfeeding However, by the late 40s to early 50s, menopause begins, causing fluctuations and a dramatic decrease in estrogen levels This reduction diminishes estrogen's stimulation of breast glandular tissue, resulting in dehydrated and inelastic connective tissue Consequently, breast tissue, once prepared for milk production, shrinks and loses shape, becoming predominantly composed of fatty and stromal tissues.
Principal risk factors for breast cancer
Breast carcinomas originate from the epithelial cells of the breast, specifically in the lobules and terminal ducts that produce milk Uncontrolled growth of these cells can lead to breast cancer development Various factors, including growth and reproductive hormones, influence epithelial cell proliferation and may elevate the risk of cancer.
5 to ethnicity, geographic, reproductive characteristics and lifestyle related habits A number of these key elements are considered below
High breast density, characterized by increased fibro-glandular tissue and less fat, significantly raises the risk of breast cancer in women In the United States, women with high mammographic density face a four to six times greater risk of developing breast cancer compared to those with low density Similarly, research in Singapore indicates that women with over 75% mammographic density are three times more likely to develop breast cancer than those with less than 10% density, although their risk remains lower than that of American women In contrast, Japanese women do not exhibit a similar increased risk with densities above 75%; instead, their risk elevates with densities between 25-49% and 50-75% Additionally, younger populations in westernized countries often present higher breast density, which complicates cancer screening due to the similarity in radio-density between dense fibroglandular tissues and malignant lesions, making early detection more challenging.
6 density qualitative and quantitative assessment (BIRADS 1: Almost entirely fat; BIRADS 2: Scattered fibroglandualar density; BIRADS 3: Heterogeneously dense; and BIRADS 4: Extremely dense)
High body mass index (BMI) is linked to an increased risk of breast cancer across many countries While higher BMI appears to offer some protection against breast cancer before menopause, it is associated with a higher incidence of the disease after menopause, particularly among Caucasian women and in Korea The reasons for the differing effects of BMI on breast cancer risk in pre- and post-menopausal women remain unclear, though endogenous estrogen is believed to play a role In premenopausal women, obesity can lead to more frequent anovulatory cycles, resulting in lower levels of estrogen and progesterone receptors, which are associated with breast cancer Conversely, in postmenopausal women, excess adipose tissue may promote breast cancer cell proliferation.
Obesity can elevate endogenous estrogen levels by enhancing the activity of hormone-related enzymes This condition also results in reduced levels of sex-hormone-binding globulin (SHBG), which, coupled with increased production of oestrone and testosterone, may promote cellular growth and inhibit apoptosis in breast tissue.
In developed countries, factors such as early menarche, reduced parity, older maternal age at first birth, lack of breastfeeding, and late menopause are associated with an increased risk of breast cancer, likely due to prolonged exposure to ovarian hormones Conversely, studies of Asian populations, which generally have lower breast cancer rates, indicate that nulliparity and older age at first childbirth are linked to a higher risk, although the inverse relationship with breastfeeding is less common, likely due to the prevalent practice of extended breastfeeding among Asian women.
Family history is a significant risk factor for breast cancer, with approximately 10% of cases linked to genetic mutations Women with a mother or sister diagnosed with breast cancer face a notably higher risk The primary genes associated with hereditary breast cancer are BRCA1 and BRCA2, and those with a strong family history often receive a diagnosis at a younger age than the general population While family history is strongly correlated with breast cancer in Western populations, studies indicate it is less significant among Chinese and Iranian women.
Research indicates that women in Western countries who undergo hormone replacement therapy for over four years face a 35% increased risk of breast cancer, a risk that diminishes within five years after discontinuation However, this trend has not been observed in Asian populations Additionally, a systematic review of 34 case-control studies from 1980 to 2002 found that women who used oral contraceptives had a 17% higher risk of breast cancer compared to non-users, with pooled odds ratios of 1.07 for Western women and 1.17 for Asian women, although these figures did not achieve statistical significance This discrepancy may be attributed to the lower hormone levels in occasional oral contraceptive use compared to full hormone replacement therapy, highlighting the need for further research on the effects of more frequent oral contraceptive use.
Lifestyle factors, for instance, tobacco smoking, alcohol intake, physical activity and several diet factors have been recorded with associations with breast cancer These elements are discussed in details below
Women who are actively exposed to tobacco face an increased risk of developing breast cancer, with those starting to smoke at a young age having their risk heightened by 20% Recent research indicates that prolonged tobacco use can escalate this risk by as much as 50%.
Smokers who inhale high levels of NAT2, an enzyme involved in the metabolism of aromatic amines found in various tobacco carcinogens, may face increased cancer risks While smoking is recognized as a risk factor for breast cancer among Western women, studies indicate that this association is not as significant in Asian populations, likely due to lower smoking rates among Asian women.
Epidemiological studies indicate a positive correlation between alcohol consumption and breast cancer risk in Caucasian and African women, with a meta-analysis revealing that women who drink face a 22% higher risk of diagnosis compared to non-drinkers, regardless of alcohol type The oncogenic effects of acetaldehyde and oxygen radical metabolites from alcohol may contribute to this increased risk, alongside potential nutritional deficiencies and immune system alterations that heighten breast cells' susceptibility to carcinogenesis Regular alcohol intake is a significant risk factor for breast cancer among Asian-Americans and Japanese-Americans born in the U.S., although this trend does not appear in women from China These varying effects of alcohol on breast cancer risk across different populations underscore the importance of examining this modifiable lifestyle factor within specific demographic groups.
Numerous studies have examined the link between physical activity levels and breast cancer risk, revealing that women engaging in vigorous-intensity exercise experience a 25% reduction in risk compared to inactive women, according to 47 out of 62 studies The biological mechanisms by which physical activity may help prevent breast cancer are still being explored.
Engaging in regular physical activity can significantly lower the risk of breast cancer by influencing reproductive factors, such as delaying the onset of menstruation and regulating menstrual cycles High levels of exercise may inhibit breast cancer development by reducing sex hormone levels, decreasing body fat, lowering insulin levels—which is a growth factor for epithelial cells—and boosting the immune system.
While vegetable consumption is often believed to reduce breast cancer risk in women due to its antioxidant and fiber content, many studies have not demonstrated a significant protective effect Specifically, an analysis of prospective cohort studies found no notable impact of fiber on cancer prevention, despite theories suggesting it could inhibit cancer by binding carcinogens and estrogens for elimination However, a higher intake of dietary patterns rich in vegetables, fruits, and soy has been linked to a decreased risk of breast cancer among postmenopausal women in Singapore and China.
Isoflavones found in soy products are natural phytoestrogens that resemble estrogen in chemical structure These compounds can compete for estrogen receptors, which may reduce the effects of stronger estrogens and subsequently lower the risk of breast cancer A comprehensive review of over ten studies involving both Caucasian and Asian women revealed a 5% decrease in relative breast cancer risk for each increase in soy isoflavone intake.
A recent meta-analysis indicates that postmenopausal Asian women who consume high amounts of soy may experience a significant reduction in breast cancer risk In contrast, the same study found no significant relationship between soy intake and breast cancer risk among Western populations, likely due to their lower average soy consumption.
Previous findings about breast cancer risk factors in Vietnam
Breast cancer risk factors are well-documented in developed countries, but in Vietnam, knowledge about these elements remains limited Two studies have examined various risk factors associated with female breast cancer in the country The first study focused on identifying these factors and their implications for public health.
The age at first menarche, total months of lactation, and breast cancer incidence were not reported in the study Additionally, Ginsburg and colleagues found no significant associations between BRCA mutations, family history, and breast cancer among 298 women in Hanoi, Vietnam These contrasting findings regarding breast cancer risk factors between Vietnamese and Caucasian women highlight the necessity for tailored approaches to understanding breast cancer risks.
Mammographic density, a significant factor linked to breast cancer risk, remains unexplored among Vietnamese women Research indicates that women in westernized nations with dense breast tissue face a higher risk of breast cancer, as high-density mammograms often obscure subtle lesions Given that young Vietnamese women typically have a greater amount of fibroglandular tissue and that the peak age for breast cancer in Vietnam is younger than in western countries, assessing mammographic density is crucial This evaluation is essential for determining the effectiveness of mammography in Vietnam's national breast screening program, which is currently absent in this developing Southeast Asian nation.
Deficiencies in the literature
Although there were a couple of studies assessing several factors related to breast cancer in Vietnam, these studies had limitations in terms of sample size or mixed sample approach,
A study examining the relationship between various risk factors and breast cancer tumor markers in premenopausal women from Vietnam and China found no significant associations with BMI, age, menarche, lactation duration, or BRCA mutations Due to the inclusion of both Vietnamese and Chinese participants, drawing specific conclusions for Vietnam was challenging Another study investigated genetic and hereditary factors related to breast malignancy but also found no significant links, primarily due to a limited number of BRCA positive cases, with only two pathogenic mutations identified among 259 patients (one in BRCA1 and one in BRCA2).
Breast density and lifestyle factors, significant agents in breast cancer risk, remain underexplored, particularly in non-Caucasian populations Most epidemiological studies have concentrated on Caucasian women, revealing that findings in Asian countries may differ due to genetic and lifestyle variations that influence breast cancer susceptibility The Million Women Study, conducted by Oxford University, highlighted that Asian and African women are 18% and 15% less likely to develop breast cancer than their Caucasian counterparts, with lifestyle differences accounting for much of this disparity Given these ethnic variations, it is crucial to conduct research on breast cancer risk factors in countries like Vietnam to validate data from Western studies.
Aim and objectives
The aim of this thesis is to investigate risk factors of breast cancer among Vietnamese women The objectives are:
1 To conduct a literature review about female breast cancer incidence in Vietnam, comparing with the situation in other Asian countries
2 To identify the relationship of breast density, demographic, reproductive and lifestyle factors with breast cancer among Vietnamese women
3 To examine the association of mammographic density with known and suspected risk factors for breast cancer
This study aims to investigate the distribution of breast cancer risk factors among women in northern and southern Vietnam, enhancing our understanding of the differing breast cancer incidence rates observed between these two regions.
Structures
This thesis evaluates the relationship between breast density, demographic factors, reproductive history, and lifestyle choices in relation to breast cancer among Vietnamese women The study is structured systematically to present its findings.
Chapter 1 (the current chapter) provides an overview of the thesis background and its purposes
Chapter 2 provides a comprehensive literature review on the incidence of breast cancer among Vietnamese women, comparing it to rates in other Southeast Asian and Asia Pacific countries It summarizes previous research findings regarding breast cancer risk in Vietnam This chapter was published in the peer-reviewed journal Cancer Biology & Medicine, under the citation: Trieu PD, Mello-Thoms C, Brennan PC "Female breast cancer in Vietnam: A comparison across Asian specific regions," Cancer Biology & Medicine 2015, 12(3): 238.
Chapter 3 presents a case-control study that explores the association between established and potential risk factors, including demographic, reproductive, and lifestyle characteristics, and breast density in relation to breast cancer among Vietnamese women This research was published in Cancer Research and Treatment by Trieu PD, Mello-Thoms C, Peat J, Do DT, and Brennan PC, highlighting the risk factors for female breast cancer in Vietnam.
Cancer Res Treat 2017, doi: 10.4143/crt.2016.488
Chapter 4 presents a study examining the relationship between breast density and various established and potential risk factors for breast cancer in Vietnam This research was published in the Asia Pacific Journal of Public Health, authored by Trieu PD, Mello-Thoms C, Peat J, Do DT, and Brennan PC.
Associations of breast density with demographic, reproductive and lifestyle factors in a developing South East Asian population, Asia Pacific Journal of Public Health 2017, 29
16 cancer risk factors in the north and the south of Vietnam Chapter 5 was published in
The study published in the Asia Pacific Journal of Cancer Prevention by Trieu PD, Mello-Thoms C, Peat J, Do DT, and Brennan PC in 2017 highlights the inconsistencies in breast cancer risk factors between the northern and southern regions of Vietnam This research emphasizes the need for region-specific strategies in breast cancer prevention and awareness, acknowledging the diverse environmental and lifestyle factors that influence cancer risk across different areas of the country.
Chapter 6 presents a discussion reviewing the thesis findings, potential implications and future research direction
Each chapter begins with a bridging section, while the appendices at the end of this thesis include conference presentations, study materials, and journal submission guidelines for authors.
Confirmation of co-authors about authorship contribution of the PhD candidate
As co-authors of the paper titled “Risk Factors of Female Breast Cancer in Vietnam: A Case-Control Study,” we acknowledge that Phuong Dung (Yun) Trieu played a pivotal role in the research and findings presented in this study.
Conception and design of the work
Data collecting, analysis and interpretation
Drafting the article and critical revision for the content
A/Professor Claudia Mello-Thoms Date
Dr Do Doan Thuan Date
Bridging section for chapter three
The rise in breast cancer cases in developing countries over recent decades highlights a critical gap in research, as there are few studies that comprehensively identify risk factors associated with the disease Understanding the etiology of breast cancer in these populations is crucial for determining specific risks, which can lead to improved screening methods for women in low-risk areas and better identification of those at high risk.
Breast cancer risk factors include mammographic density, reproductive history, lifestyle choices, diet, hormone use, and genetic predisposition While many studies focus on Western women, research on Asian populations is limited and inconsistent For instance, a low number of pregnancies affects both Caucasian and Asian women similarly, but hormone replacement therapy impacts Caucasian women more significantly A recent study in Bangladesh found that, aside from age at menarche and Body Mass Index (BMI), other established risk factors from Western populations do not apply to the younger demographic in this developing South Asian country.
Breast cancer risk factors studied in Western women may not apply to Vietnamese women, who often experience earlier onset and later diagnosis Limited epidemiological research has highlighted discrepancies in hereditary and reproductive factors compared to Western populations, while other significant elements such as breast density and lifestyle have yet to be explored Given the lack of evidence regarding relevant risk factors for Vietnamese women, a comprehensive study is crucial Our research employed a case-control design at Vietnam's largest cancer screening and treatment centers, investigating a wide range of risk factors, including for the first time in Vietnam, the relationship between mammographic density, lifestyle factors, and breast cancer This study aimed to address limitations of previous research using validated metrics and methods from extensive breast cancer studies.
Confirmation of co-authors about authorship contribution of the PhD candidate
In the paper titled “Associations of breast density with demographic, reproductive, and lifestyle factors in a developing South East Asian population,” we acknowledge that Phuong Dung (Yun) Trieu played a pivotal role in the research, significantly contributing to the study's findings and insights.
Conception and design of the work
Data collecting, analysis and interpretation
Drafting the article and critical revision for the content
A/Professor Claudia Mello-Thoms Date
Dr Do Doan Thuan Date
Bridging section for chapter four
Breast density is defined by the presence of fibroglandular tissues that appear radiographically dense and radio-opaque on mammograms, in contrast to fatty tissues that are radiolucent and considered non-dense High mammographic density is recognized as a significant indicator of breast cancer risk among Vietnamese women, aligning with findings from Western countries; however, the risk magnitude in Vietnam is notably lower, with an Odds Ratio of 1.7 compared to 3-6 in Western nations Identifying factors associated with breast density, some of which may be modifiable, could enhance breast cancer prevention strategies Despite limited knowledge on mammographic density in Vietnamese women, insights from other countries provide valuable context.
Previous research indicates a significant link between breast density and various breast cancer risk factors High genetic inheritance levels contribute to similarities in mammographic characteristics, highlighting the crucial role of heredity in determining breast density.
Studies indicate that heritability accounts for over 50% of the differences in mammographic density among twins While genetic factors play a significant role, other influences are also important Specifically, lower mammographic density is associated with older age, being overweight, postmenopausal status, and having had more live births It is believed that age and reproductive factors may affect mammographic density through hormonal mechanisms that influence breast cell growth Interestingly, endogenous sex hormones do not appear to correlate with breast density in postmenopausal women, highlighting the complexity of these relationships.
57 sex hormones in high mammographic density was reported among women using hormone replacement therapy 12, 13
Menstrual and reproductive factors vary significantly across races and generations, with women born in recent decades or in westernized countries tending to experience earlier menarche, later childbirth, fewer children, and shorter lactation periods compared to those from earlier generations or Asian countries These disparities lead to inconsistent findings regarding the relationship between mammographic density and reproductive factors across different ethnicities Therefore, understanding the connection between these elements and mammographic density requires careful consideration of both age and race.
Research indicates that Body Mass Index (BMI) significantly influences breast density, with overweight women often exhibiting lower mammographic density due to a higher proportion of fatty tissue in their breasts Additionally, postmenopausal women who are overweight may experience elevated estrogen levels from breast fatty tissues, potentially impacting the amount of dense breast tissue Given that women in Vietnam and other developing Asian countries generally have lower BMI compared to their counterparts in Western countries, there is a pressing need for country-specific studies to explore these differences further.
Lifestyle factors, including physical activity, vegetable consumption, alcohol intake, and smoking, may influence breast cancer risk through their effects on mammographic density However, research on the relationship between breast density and these lifestyle factors has produced mixed results, raising questions about the potential impact of ethnicity and race on these associations Furthermore, high levels of physical activity are believed to play a protective role against breast cancer.
Research indicates that reducing body fat and insulin levels can enhance the immune system However, numerous studies have found no significant correlation between physical activity and mammographic density in Caucasian women from high-risk countries In contrast, the relationship remains ambiguous for Asian women in developing countries, who typically engage in higher levels of physical activity despite being classified as low-risk populations.
Research suggests a potential link between alcohol consumption and breast density, as higher alcohol intake has been associated with an increased risk of estrogen receptor-positive (ER+) breast cancer Studies from the US and Sweden indicate that women who consume alcohol may exhibit greater breast density compared to abstainers, although not all studies support this finding The discrepancies in results could stem from varying sample sizes, diverse study populations, or different methods of measuring alcohol consumption Additionally, it remains unclear how cultural factors, such as those in countries like Vietnam where alcohol consumption is viewed as unfeminine, might influence the relationship between drinking and breast density.
Research indicates that smoking may have an anti-estrogenic effect, with some studies showing that smokers exhibit lower breast density compared to non-smokers, while other studies found no correlation Additionally, a negative association between vegetable consumption and mammographic density was observed in US premenopausal women; however, no such relationship was found among Japanese women, potentially due to variations in vegetable types and cooking methods.
Vietnam has been experiencing a rapid increase in breast cancer incidence rate in the last few decades 33 Thus identifying features related to breast density, one of the most essential
Breast cancer indicators for women are a significant public health concern, particularly in developing Asian countries where awareness of the connection between breast cancer risk factors and breast density is limited Most clinical procedures and healthcare strategies in these regions are based on findings from Caucasian populations, which may not be applicable to Vietnamese women Research has shown that the distribution of breast cancer risk factors differs between Vietnamese and westernized women, highlighting the need for a better understanding of mammographic density specific to this demographic Currently, there is a lack of studies investigating mammographic density in Vietnamese women, making the relevance of Western data to Vietnam uncertain.
The next phase of this research focused on examining the relationship between demographic, reproductive, and lifestyle factors with breast density, while also investigating the links between these factors and breast cancer within specific density categories The study involved 1,651 Vietnamese women, including 345 breast cancer cases and 1,306 controls.
Confirmation of co-authors about authorship contribution of the PhD candidate
As co-authors of the paper titled “Inconsistencies of Breast Cancer Risk Factors between the Northern and Southern Regions of Vietnam,” we acknowledge that Phuong Dung (Yun) Trieu played a pivotal role in making significant contributions to the research.
Conception and design of the work
Data collecting, analysis and interpretation
Drafting the article and critical revision for the content
A/Professor Claudia Mello-Thoms Date
Dr Do Doan Thuan Date
Bridging section for chapter five
Over the past two decades, Vietnam has witnessed a significant rise in breast cancer diagnoses, particularly in the southern region, where Ho Chi Minh City's incidence rate increased from 12.2 to 19.4 per 100,000 women In contrast, Hanoi's rate rose from 26.7 to 29.7 per 100,000 women during the same period This trend may be attributed to heightened awareness and improved diagnostic systems among Vietnamese women and healthcare professionals However, the reasons behind the more rapid increase in breast cancer cases in southern Vietnam compared to the north remain unclear.
Hanoi and Ho Chi Minh City are Vietnam's two largest cities, each with a population of around 7 million and over 90% Kinh ethnicity Serving as the main commercial, cultural, and medical hubs for the northern and southern regions, these cities exhibit notable differences in history, geography, and lifestyle despite their similar demographics.
The southern region of Vietnam experienced greater devastation during the Vietnam War (1961–1971) compared to the north Approximately 75 million liters of Agent Orange, a highly toxic herbicide containing chlorinated dioxins, were sprayed over 20% of southern Vietnam's land, affecting around 4.5 million Vietnamese residents The exposure to these toxic chemicals has had severe and lasting consequences on the health and environment of the region.
The health impacts during the war period have been scrutinized, particularly concerning TCDD (Tetrachlorodibenzo-p-dioxin), a contaminant in Agent Orange linked to cancer and birth defects However, studies found no correlation between DDT (Dichlorodiphenyltrichloroethane)/DDE (Dichlorodiphenyldichloroethylene), which share structural similarities with TCDD, and breast cancer risk among Vietnamese women, suggesting that the influence of war agents can be excluded.
Differences in breast cancer incidence patterns between northern and southern Vietnam can be attributed to lifestyle variations influenced by cultural factors Northern populations tend to maintain traditional habits shaped by centuries of Northeast Asian influence, while southern populations have increasingly adopted Western lifestyles due to historical interactions and rapid urbanization Research indicates that these lifestyle differences, including reproductive behaviors, correlate with varying breast cancer risk factors across regions For instance, southern Vietnamese women have fewer live births on average (1.7) compared to their northern counterparts (2.6) Furthermore, an increase in breast cancer cases among Vietnamese women who migrate to Western countries, such as the United States, underscores the impact of acculturation on cancer development This highlights the significance of geographic and non-genetic factors in breast carcinogenesis, while also pointing out the lack of epidemiological studies comparing the two regions as a critical obstacle in developing effective breast cancer screening strategies.
This study aims to address the lack of information regarding risk factors for female breast cancer by analyzing data from the initial research conducted in Chapter 3 The focus is on identifying differences in the presentation of these risk factors between northern and southern Vietnam.
1 Duc NB TT, Can DT, Dieu B, Nga NTH, Thang ND Situation of female breast cancer in some provinces and cities period 2001–2007 Viet J Oncol (in Vietnamese) 2009;1:5-11
2 Anh PT, Parkin DM, Hanh NT, Duc NB Cancer in the population of Hanoi, Vietnam, 1988-1990 Br J Cancer 1993;68(6):1236-42
3 Nguyen QM, Nguyen HC, Parkin DM Cancer incidence in Ho Chi Minh City, Viet Nam, 1995-1996 Int J Cancer 1998;76(4):472-9
4 Trieu PD, Mello-Thoms C, Brennan PC Female breast cancer in Vietnam: a comparison across Asian specific regions Cancer Biol Med 2015;12(3):238-45
5 Nhu DD, Kido T, Naganuma R, Sawano N, Tawara K, Nishijo M, Nakagawa H, Hung NN, Thom le TH A GIS study of dioxin contamination in a Vietnamese region sprayed with herbicide Environ Health Prev Med 2009;14(6):353-60
6 R L High dioxin dose linked to cancer Science 1991;251(4994):625
A study published in the American Journal of Public Health by Schecter et al examines the long-lasting effects of Agent Orange on Vietnamese populations, highlighting the persistence of elevated dioxin levels in human tissues The research underscores the ongoing health risks associated with exposure to this chemical, emphasizing the need for continued monitoring and public health interventions.
8 Schecter A, Toniolo P, Dai LC, Thuy LT, Wolff MS Blood levels of DDT and breast cancer risk among women living in the north of Vietnam Arch Environ Contam Toxicol
A study by Lea CS et al examined the reproductive risk factors for breast cancer among middle-aged women in Marin County, California, comparing them to a sociodemographically similar region in Northern California The findings highlight significant differences in these risk factors, contributing to a better understanding of breast cancer prevalence in varying populations This research underscores the importance of localized studies in identifying specific health risks associated with breast cancer.
10 Lee H, Li JY, Fan JH, Li J, Huang R, Zhang BN, Zhang B, Yang HJ, Xie XM, Tang ZH, Li H, He
JJ, et al Risk factors for breast cancer among Chinese women: a 10-year nationwide multicenter cross-sectional study J Epidemiol 2014;24(1):67-76
11 Teerawichitchainan B, Amin S The role of abortion in the last stage of fertility decline in Vietnam Int Perspect Sex Reprod Health 2010;36(2):80-9
12 Le GM, Gomez SL, Clarke CA, Glaser SL, West DW Cancer incidence patterns among Vietnamese in the United States and Ha Noi, Vietnam Int J Cancer 2002;102(4):412-7
Asian Pacific Journal of Cancer Prevention, Vol 18 2747
DOI:10.22034/APJCP.2017.18.10.2747 Breast Cancer Risk Factors in the Northern and Southern Vietnam
Breast cancer is currently known as the most common cancer affecting Vietnamese women (Ferlay et al., 2015)
Breast cancer incidence among women in Vietnam, though relatively low at 23 per 100,000 compared to 120 per 100,000 for Caucasian women (WHO, 2012), has surged by approximately 45% over the past decade, rising from 16 per 100,000 in 2002, making it the most common carcinoma among Vietnamese women (Duc NB, 2009) Furthermore, the rates of breast cancer vary significantly across different regions in Vietnam, indicating a geographic disparity in incidence.
Hanoi and Ho Chi Minh City (HCMC) are the largest cities in northern and southern Vietnam, respectively, with comparable populations and ethnicities However, during the 1990s, Hanoi reported a breast cancer incidence rate of 26.7 per 100,000, which was double that of HCMC's rate of 12.2 per 100,000 (Nguyen et al., 1998; Anh and Duc, 2002).
Interestingly however since that time, the rate of new
Recent studies indicate a rising trend in breast cancer cases in southern Vietnam compared to the north, prompting an investigation into regional risk factors and the influence of westernization Data from 2015, collected from the largest oncology hospitals in both regions, included information on breast density, demographics, reproductive history, and lifestyle factors from 127 northern and 141 southern breast cancer cases, alongside matched controls Significant findings revealed that northern women faced increased risks associated with early menstruation (OR=2.1; P