A review of cervical cancer incidence and HPV infection

JOURNAL OF MEDICAL RESEARCH

A REVIEW OF CERVICAL CANCER INCIDENCE
AND HPV INFECTION
Ngo Van Toan, Nguyen Duc Hinh, Luu Thi Hong, Vu Hong Thang, Bui Van Nhon
Hanoi Medical University
This review was carried out to provide information regarding cervical cancer incidence and Human Papilloma
Virus (HPV) infection worldwide as well as in Vietnam. Cervical cancer is the second most common cancer
in women in less developed regions of the globe. An estimation of 445 000 new cases occurred in women
from low - and middle-income countries in 2012, comprising 84% of all new cases of cervical cancer worldwide that year. In 2012, approximately 270 000 women died from cervical cancer; more than 85% of these
deaths occurred in low - and middle - income countries. There are more than 100 types of HPV, of which at
least 13 are cancer-causing. Cervical cancer is caused by sexually acquired infections from certain types of HPV.
Two types of HPV (strains 16 and 18) cause 70% of all cervical cancers and precancerous cervical lesions.

Keywords: Cervical cancer, incidence, HPV

I. INTRODUCTION

develop active intervention programs, the

Cervical cancer occurs in tissues of the

number of cervical cancer cases will increase

cervix (the organ connecting the uterus and

by an additional 25% in the next 10 years

vagina). It is usually a slow-growing cancer

worldwide [1]. In England, since the 1970s, the

that may not present with symptoms but can

cervical cancer incidence rate has been

be found with regular Pap tests (a procedure

decreasing (it reduced 63% during 1985 -

in which cells are scraped from the cervix and

1987 and 66% during 2009 - 2011, compared

looked at under a microscope). Cervical

to the 1970’s) [1]. Developing countries must

cancer is almost always caused by human

implement better cervical cancer screening

papillomavirus (HPV) infection. Among more

programs to see a similar reduction in cancer

than 100 types of HPV, several types can

cases. The objective of this review was to

cause cervical cancer. The most common

provide the information regarding cervical

types that lead to cervical cancer are HPV 16

cancer incidence and HPV infection worldwide

and 18. Over the past 40 years, the incidence

and specifically in Vietnam.

of cervical cancer has reduced significantly
in developed countries due to implementation
of cervical cancer screening programs. In
developing countries, the cervical cancer
incidence

rate

has

remained

stable

or

increased. If developing countries do not

II. CONTENTS

1. Incidence rate
1.1. Cervical cancer incidence rates
worldwide
Cervical

Corresponding author: Ngo Van Toan, Hanoi Medical
University
Email:
Received: 04 November 2016
Accepted: 10 December 2016

JMR 105 E1 (7) - 2016

cancer

is

the

second

most

common kind of cancer among women worldwide after breast cancer. There were about
528,000 new cases worldwide and 260.000
women died of cervical cancer [1]. More than

1

JOURNAL OF MEDICAL RESEARCH
80% of infected and affected women live in the

Almost all cervical cancer cases were in

developing countries. Cervical cancer is the

women aged 30 and above. The age-

fourth leading cause of death among women

standardized incidence rate of cervical cancer

globally. About 20% of new cases worldwide

among white women was from 8.2 to 8.8

were

In

cases per 100,000 women, while in black

Sub-Sahara countries, there are about 34.8

women it was 6.3 - 11.2 per 100,000 women,

new cases of cervical cancers per 100,000

and among Asian women it was 3.6 - 6.5 per

women and 22.5 deaths due to cervical cancer

100,000 women [5 - 9].

diagnosed

in

India

[2].

per 100,000 women per year [3; 4].

Approximately 6,000 new cervical cancer

In contrast, there were 6.6 new cases of

cases are diagnosed annually in South Africa

cervical cancers per 100,000 women and 2.2

(SA) [1]. Accurate contemporary data on

deaths due to cervical cancer per 100,000

cervical cancer incidence has not been

women per year in the North America [1]. In

available since the 1999 Cancer Registry was

the United States, the age - standardized rate

published. Many cases were presumed to still

of cervical cancers was 9.6 cases per 100,000

be undiagnosed due to poor screening programs

women during the period of 1996 - 2000 [1].

and more than half of all patients diagnosed

The global survival rate of cervical cancer five

each year are expected die from the disease.

years after being diagnosed was 72%. There

The World Health Organization estimated the

were about 4,100 women that died due to cer-

age-standardized incidence rate for SA to be

vical cancer in 2003 in the United States [1].

26.6 per 100 000 women [1]. The current

Cervical cancer was the sixth most common

prevalence of pre - invasive cervical disease in

cancer among female cancers in European
countries, with 58,400 new cases in 2012 [1].
The highest incidence rate of cervical cancer
was in Rumania and the lowest was in
Switzerland [1]. Cervical cancer was the
twelfth most common cancer among women in
England with an incidence rate of 10 cases
per

100,000

women

annually

[1].

The

difference in incidence rates of cervical cancer
between developed and developing countries
was due to a lack of access to screening,
early detection and treatment programs in
developing countries. In addition, other factors
such as traditional practices, poor hygiene,

and unsafe sex also contributed to high
incidence rates in developing countries.
Cervical cancer incidence is closely related
to a woman’s age.
2

SA is unknown. Data from studies published in
SA suggest important regional differences
across the country, and an overall increase in
the prevalence of cytological abnormalities
when compared with historical data. Because
of the low sensitivity of cytology, we can
assume that the true prevalence of pre invasive disease is underestimated. Moreover,
a single test done by cervical cytology, even if
done completely correct, will probably identify
fewer than half of all existing pre-invasive
cervical disease when measured against the
greater yield obtained by colposcopy and
directed biopsy. The incidence rate of cervical
cancer in Senegal was quite high at 19.4
cases per 100.000 women [10]. This rate was
1.5 times higher than breast cancer incidence
and more than 3 times higher than liver cancer
incidence among women in the country [10].
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JOURNAL OF MEDICAL RESEARCH
Cervical cancer is a common cancer

for over three years), the increased rates of

among women in developing countries in Asia.

cervical cancer in indigenous women reflects

Worldwide,

poorer access to cervical cytology screening

the

region

comprising

Asia

Oceania covers a vast and diverse area
geographically

and

ethnically,

programs [12; 13].

supporting

In contrast, in Thailand and the Phillipines,

around 60 percent of the world’s population

there have not been significant reductions in

and contributing to just over half of the global

incidence and mortality rates, despite the

burden of cervical cancer [11].

cervical

cytology

programs

that

these

India, in particular, has one of the highest

countries have had in place for decades [14].

reported cervical cancer incidence and mortal-

This perhaps reflects the fact that the

ity rates in the region. These higher rates re-

organized programs in these countries are not

flect an overall lack of widespread screening

reaching

and treatment facilities, as well as a greater

appropriate populations. As cervical cancer

proportion of persistent HPV infections, as

screening

indicated by the very high rates of cervical

sophisticated in more affluent and urbanized

cancer in older women.

Asia-Pacific countries such as Singapore,

Across the Asia Pacific region, examples of
successful cervical cytology programs are
rather limited [14]. In Australia and New Zealand, where long-standing and highly effective
cytology programs have been in existence for
several decades, incidence and mortality rates

high

proportiontions

programs

have

of

become

the
more

Hong Kong, Taiwan and Iran, cervical cancer
incidence and mortality rates have begun to
decline. Assisting further with the cervical
cancer decline in these States is the fact that
the programs in these countries are rolled out
on a national level [9; 15 - 17].

have declined

According to estimates, the incidence rate

significantly [12; 13]. In Australia in 2003, the

of cervical cancer in Indonesia was about 100

age-standardized incidence of cervical cancer

- 190 cases per 100,000 women [18]. Cervical

was 7.0 cases per 100, 000 women and the

cancer was the most common malignancy

mortality rate was 2.2 cases per 100,000

among women in Indonesia, comprising up to

women [12]. It is noteworthy, however, that

22.5% of all cancer cases reported in govern-

notwithstanding the success of the National

mental hospitals there [18]. However, this

Cervical Screening Program in the general

number

population, indigenous women in Australia

because only 25 - 30% of all sick people in

were over four times more likely to die of

Indonesia enter these medical facilities [18].

of

cervical cancer

cases

was

likely

an

underestimation,

cervical cancer than non-indigenous women in

Cervical cancer is a major health problem

2001-2004; cervical cancer incidence was 4 -

in Indonesia since most patients present in the

5 fold higher in indigenous women over the

later stages of the disease, in low resource

same time period [12]. Whilst overall for the

settings where no screening programs are

Australian population, the estimated lifetime

available. The association of the high-risk

cervical cancer screening participation rate

strains of HPV (notably strains 16, 18, 31 and

was 88 per cent (62% for over two years, 73%

45)

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with

cervical

cancer

among

female

3


JOURNAL OF MEDICAL RESEARCH
patients in Indonesia is now widely accepted,

lowest in Thai Nguyen province (4.1 cases per

as these strains of HPV have been detected in

100,000 women during 2006 - 2010) and Thua

almost all cervical cancer patients and are

Thien Hue province (5.8 cases per 100,000

much less common in women without cervical

women in 2008) [20].

cancer [18; 19].

Viet Nam has a population of 30.77 million

The distribution of HPV strains in Indonesia

women aged 15 years and older who are at

is largely unknown. HPV 18 has been reported

risk of developing cervical cancer, and this

to play more of a role in the spread of cervical

poses a major public health problem for the

cancer there than HPV 16 [18], at a rate that is

country. Current estimates indicate that every

higher than that reported in other geographical

year 5174 women are diagnosed with cervical

areas worldwide. The viral origin for cervical

cancer and 2472 die from the disease, with an

cancer and its high morbidity and mortality

estimated age - standardized incidence rate of

figures give cause for the development of a

11.5 cases per 100,000 women [20]. However,

vaccine against HPV. To design vaccines suit-

these statistics were derived by modeling

able for the Indonesian female population, an

based on data obtained from some of the

inventory of HPV prevalence is essential.

cancer treatment centers and may not reflect

1.2. The incidence rate of cervical
cancer in Vietnam
Up to now, studies on the incidence rate of

the actual rates in the country. Reports from
cancer registries operating in the country’s two
major cities, Hanoi and Ho Chi Minh City,

cervical cancer in Vietnam have been rela-

published nearly 15 years back show signifi-

tively limited. The Program for Cancer Control

cant regional variations in cervical cancer inci-

has conducted studies looking at rates of cer-

dence. The age - standardized incidence rate

vical cancer in cities and provinces across the

of cervical cancer in Hanoi, a city situated in

country since 2008. Results have shown that

Northern Vietnam, was only 6.5 cases per

the estimated crude rate of cervical cancer

100,000 women, in stark contrast to the high

was 13.1 cases per 100,000 women in 2000

incidence rate in Ho Chi Minh City, situated in

and 12.7 cases per 100,000 women in 2010.

Southern Vietnam, where the rate was 26

The age - standardized rate of cervical cancer

cases per 100,000 women [21; 22]. No recent

was 17.3 cases per 100,000 women in 2000

data

and 13.6 cases per 100,000 women in 2010.

mortality

The incidence rate of cervical cancer is

population - based cancer registries in Hanoi

different between regions and provinces. The

and Ho Chi Minh City. To develop a public

rate was highest in Ho Chi Minh City (19.7

health strategy for cervical cancer prevention

cases per 100,000 women in 2009 - 2010),

and to monitor its health impacts, Vietnam

followed by Can Tho City (17.7 cases per

must have quality data on cervical cancer

100,000 women in 2008 - 2009), then Hanoi

incidence and mortality in the population. Post

City (10.5 cases per 100,000 women during

-treatment

2004 - 2008) and finally Hai Phong (8.3 cases

determined, as this is an important indicator of

per 100,000 women in 2008). The rate was

the quality of treatment services in the country.

4

on

cervical
has

cancer

been

survival

incidence

published

rates

must

and

from

also

JMR 105 E1 (7) - 2016

the

be


JOURNAL OF MEDICAL RESEARCH
Both primary and secondary prevention

precancerous lesions and invasive cervical

strategies are highly effective against cervical

cancer [24; 25], compared with cytology -

cancer. Primary prevention via the HPV

based screening in women older than 30. Re-

vaccine is still out of bounds for the national

cently, this finding has also been confirmed in

program of Vietnam, principally due to its high
cost. However, secondary prevention through
cervical cancer screening is an important
public health measure that Vietnam should
invest in. The guiding principle of secondary

India, the developing country with a low human immunodeficiency virus (HIV). Over the
last 20 years, the widespread HIV epidemic

has increased the overall burden of HPV infec-

prevention of cervical cancer is that the

tion in sub - Saharan Africa. Accurate current

disease should be detected through system-

knowledge about hrHPV prevalence in devel-

atic screening of all women within a certain

oping countries is essential for cost analysis

age group, and that all women found to have

and planning for regionally tailored national

pre - cancerous lesions should be treated.

prevention and screening programs.

Cervical cancer precursors are classified as
Cervical Intraepithelial Neoplasia (CIN) 1, CIN
2 or CIN 3 depending on the extent of the disease in the epithelium. Whereas most CIN 1
lesions are due to transient HPV infection and
do not progress further, a large number of CIN
2 and CIN 3 lesions will progress to invasive
cancers if left untreated [23]. In Vietnam, there
is paucity of data regarding the population

prevalence of CIN 2 and CIN 3 - information
that is necessary to understand the disease
burden in the country, to formulate prevention
strategies, and to design future interventions
related to cervical cancer screening.

2.1. Human papillomavirus: the etiological agent of cervical cancer
Molecular epidemiological studies have
conclusively established the causal association between high - risk HPV genotypes and
cervical cancer. The relative risk of developing
cervical cancer from high - risk HPV strains is
in the hundreds - fold and far greater than the
association between cigarette smoking and
lung cancer. In fact, cervical cancer is the first
cancer to be 100 percent attributable to an
infection [24; 25]. Papillomaviruses are a very
heterogeneous group of viruses. They are
widely distributed throughout nature, infecting
not only humans but also other higher

2. HPV infection and cervical cancer
The identification of high-risk HPV (hrHPV)
types (the strains of HPV that cause cervical
cancer) offers the prospect of improving
cervical screening programmes through the

vertebrates such as dogs, horses, and cattle.
In general, they are highly species-specific,
with each animal species having its own
papillomavirus [for example, bovine papillomaviruses (BPV) of cattle is different from

introduction of hrHPV - based screening tests.

HPV in humans]; there is no known crossing

Studies from developed countries provide

of papillomaviruses between species.

convincing evidence that hrHPV DNA - based

Sequence analysis of cloned HPVs shows

screening algorithms are cost - effective and

that they are highly conserved and that the

clinically

genome is not prone to mutation, in contrast to

sensitive

for

JMR 105 E1 (7) - 2016

the

detection

of

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JOURNAL OF MEDICAL RESEARCH
other viruses like the human immunodefi-

squamous cell carcinomas, 80 to 85 percent of

ciency virus (HIV). The 8 kilobase circular

which are adenocarcinomas which are more

genome of HPV is made up of one early (E)

difficult to detect on cytological screening.

gene (necessary for replication of the viral

Phylogenetically, HPVs are within the alpha

DNA, transcription of the non-structural early

genus. HPV genotypes 16 and 18 are quite

proteins E1, E2, E4, E5, E6 and E7, and as-

distinct and are from separate species: HPV

sembly of newly produced viral particles) and

genotype 16 is from species 9, whereas HPV

two late (L) genes (L1 and L2) (which code for

genotype 18 is from species 7. In contrast,

the proteins making up the major viral capsid).

HPV genotypes 6 and 11 are closely related

Much of the natural host immune response is

and in the same species, species 10.

directed to conformational epitopes on the L1

2.2. HPV infection

protein displayed on the outer surface of the
intact virion [26]. Moreover, the L1 protein,

HPV specifically infects the epithelial cells

when expressed via recombinant yeast or viral

of the skin or mucosa. Either through minor

vectors, folds and self - assembles into empty

abrasions of the squamous epithelium or

capsids or viral-like particles (VLPs), which

through entry at the transformation zone in the

antigenically and morphologically resemble

cervix, viral particles infect basal cellular lay-

wild virus, forming the basis of current prophy-

ers. It is here that a small amount of the viral

lactic vaccine candidates.

genome is maintained, allowing for latency in

Over 200 papillomaviruses are now recognized, and over 100 have been cloned [27;
28]. Of the large number of HPVs, there is
tropism of infection for different tissues by
various genotypes; i.e., skin types (e.g., HPV
1 - 4, 10, 26-29, 37, 38, 46, 47, 49, 50, 57)
and genital types (e.g., HPV 6, 11, 16, 18,

some infected women. Full HPV infection only
occurs when the virus enters the supra basal
compartment, where the keratinocytes lose

their ability to replicate but initiate terminal
differentiation. As the epithelium is shed, the
full virions become ready to infect the next
host.

various 30s, 40s, 50s, 60s, 70s). Around 40

It is because of this complex interaction

genotypes are able to infect the genital tract.

with the differentiating keratinocyte, that HPV

Of these, some have oncogenic potential

cannot be propagated in vitro in cell lines, in

(established high risk strains include strains

contrast to other viruses that are readily

16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59,

cultured for diagnostic purposes. However, by

68, 73, 82; probable high risk strains include

various molecular hybridization assays, HPV

strains 26, 53, 66) whilst others are low risk

nucleic acid can be detected as DNA or RNA

(established low risk strains include strains 6,

in tissues or clinical samples.

11, 40, 42, 43, 44, 54, 61, 70, 72, 81,

High-risk HPV infection is the ‘necessary’

CP6108). Within the high - risk group, HPV

cause for the development of cervical cancer

genotypes 16 and 18 impart the greatest

[29 - 31]. The International Agency for Research

degree of risk, with these now known formally

on Cancer in Lyon lists 12 genotypes of HPV

as human carcinogenic agents. HPV 16 and

that are considered high - risk and have suffi-

18 contribute to around 70 per cent of cervical

cient evidence that they cause cervical cancer:

6

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JOURNAL OF MEDICAL RESEARCH
HPV strains 16, 18, 31, 33, 35, 39 45, 51, 52,

amounts of HPV DNA is associated with an

56, 58, and 59. Only one study has been done

increased risk of the development of cervical

in Vietnam to look at the overall HPV preva-

cancer [32]. Considering the broad interest in

lence in the country’s female population. No

HPV vaccines, it is important to verify the

study has been done to date that documents

prevalence of the various types of HPV world-

HPV genotype prevalence, especially of the

wide, especially the high-risk strains. Despite

high risk types, either in the healthy female

the medical importance of identifying high-risk

population or among cervical cancer patients.

HPV strains, and the high incidence rate of

To understand how potentially impact the HPV

cervical cancer, there is a lack of information

vaccine could be in the country, the distribu-

on the incidence of the most common HPV

tion of high risk HPV genotypes among both

genotypes.

cervical cancer patients and those with CIN 2

To

determine

HPV

genotypes,

the

and CIN 3 lesions must be determined.

amplified PCR products were run in 1.5%

Knowledge regarding the prevalence of the

agarose gel stained by ethidium bromide.

high - risk HPV genotypes in CIN 2+ lesions

Since all amplified products had different

will also help to gain insight into the useful-

lengths, the genotypes of the virus were

ness of various HPV detection technologies as

analyzed by electrophoresis and visualized by

cervical cancer screening tests.

an ultraviolet light trans - illuminator. Bands of

Worldwide, the risk of cervical cancer has

appropriate size were identified by comparison

increased in parallel with the incidence of

with DNA molecular weight markers that are

certain genotypes of HPV [32]. Therefore, the

made from a set of known DNA fragments.

presence of these genotypes indicates a

The adequacy of the DNA in each specimen

significant risk factor for the development of

for PCR amplification was determined by the

cervical cancer. HPV infects cutaneous and

detection of the β - globin gene.

mucosal epithelial cells of the ano - genital

In Vietnam, at present, cervical cancer

tract, which can lead to a variety of diseases

screening activities in the country are mostly

with a range of severities. The mildest form of

opportunistic. Some of the country’s non-

HPV disease is the low - grade intraepithelial

governmental

neoplasia (CIN1). These lesions can persist

conducting

and progress to high-grade disease (CIN2)

relatively small population. Since 2007, the

and invasive cervical cancer. HPVs are also

organization Program for Appropriate Techno-

found in cancers of the tonsils, anus, penis

logy in Health (PATH) is conducting a cervical

and cancer of neck.

cancer vaccination and screening project in

voluntary
individual

organizations
projects

are

involving

High - risk HPV 16 and 18 are the most

Thanh Hoa, Hue, and Can Tho provinces, in

common causes of cervical cancer, account-

collaboration with the Vietnamese National

ing for approximately two thirds of all cervical

Institute of Hygiene and Epidemiology and the

carcinomas worldwide. Of the two strains,

Maternal and Child Health Department of the

HPV-16 occurs most frequently. Studies have

Ministry of Health. The program, primarily

shown that the presence of even minimal

relying on a ‘see and treat’ strategy using VIA

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JOURNAL OF MEDICAL RESEARCH
as the screening test, screened more than

capacity of the medical professionals linked to

38,000 women aged 30 to 49 years across

cervical

these three provinces from 2007 to February

programs in the country. In Vietnam, such pro-

2011. The Vietnamese Ministry of Health, with

fessionals include midwives, nurses, assistant

technical

physicians, obstetricians and gynecologists,

assistance

organizations,

has

from

drafted

international
the

cancer

screening

and

treatment

National

and oncologists. A KAP study in Vietnam

Population/Reproductive Health Strategy for

should be done both with women in the coun-

the period of 2011 - 2020, to be implemented

try, and with these healthcare professionals.

in 63 provinces/cities. Each province/city
developed an action plan in 2011 that

III. CONCLUSIONS

extended for five years, from 2011 to 2015.

Cervical cancer is the second most com-

Control of cervical cancer through effective

mon cancer in women in less developed re-

population - based cervical cancer screening

gions, with an estimated 445000 new cases in

programs is a major goal of the

country’s

2012 (representing 84% of the new cases

national reproductive health teams. The aim is

worldwide that year). In 2012, approximately

to screen 20% of women aged 30 - 54 years

270 000 women died from cervical cancer;

by 2015 and to scale up the program by 2020

more than 85% of these deaths occurred in

to achieve 50% coverage. The National

low- and middle - income countries. There are

Guidelines on Cervical Cancer Screening and

more than 100 types of HPV, of which at least

Treatment of Precancerous Lesions have also

13 are cancer - causing. Cervical cancer is

been prepared and advocate that VIA and/or

caused by sexually acquired infection with

cervical cytology will be offered to help screen

certain types of HPV. Two types of HPV (16

women aged 21 - 70 years.

and 18) cause 70% of all cervical cancers and

Several factors help to determine the

precancerous cervical lesions.

success of cervical cancer screening programs.
The target population must be aware of these

Acknowlegment

programs, have positive perceptions abou

We would like to express our thanks to

tpreventive health and accept screening as a

UNFPA Vietnam, the Department of Maternal

strategy to reduce cancer incidence. Even

and Child Health and the Ministry of Health for

within the same country, these factors may

their financial and technical support.

vary depending on the target population’s
ethnicity, religion, culture and literacy level. A

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