A Meta-Analysis and Systematic Review on the Association between Human Papillomavirus (Types 16 and 18) Infection and Esophageal Cancer Worldwide
A Meta-Analysis and Systematic Review on the Association between Human Papillomavirus (Types 16 and 18) Infection and Esophageal Cancer Worldwide
Jing Wang 1 2 3
Lei Zhao 1 2 3
Han Yan 1 2 3
Juanjuan Che 1 2 3
Li Huihui 1 2 3
Wu Jun 1 2 3
Bing Liu 0 1 3
Bangwei Cao 1 2 3
0 Department of Emergency, Beijing Friendship Hospital, Capital Medical University , Beijing , China
1 Funding: This study was supported by the Administration of Hospitals' Youth Programme, code: QML20150107 (to Jing Wang); The traditional Chinese medicine science and technology development fund project of Beijing (QN2015-10) (to Jing Wang); The Research Foundation of Beijing Friendship Hospital (yyqdkt2014-10) (to Jing Wang); The Capital Medical and Health Development Fund (2016) , to Jing Wang
2 Department of Oncology, Beijing Friendship Hospital, Capital Medical University , Beijing , China
3 Editor: Marcia Edilaine Lopes Consolaro, State University of Maringá/Universidade Estadual de Maringá , BRAZIL
Esophageal cancer is a common and aggressive malignant tumor. This study aimed to investigate the association between human papillomavirus (HPV) Types 16 and 18 and esophageal carcinoma (EC) in the world population by conducting a meta-analysis. Computerized bibliographic and manual searches were performed to identify all eligible literatures between 1982 and 2014. PUBMED (http://www.ncbi.nlm.nih.gov/pubmed/) and CNKI (http://www.cnki.net/) were the primary sources of case-control studies, and key words used include human papillomavirus, HPV, esophageal, esophagus, cancer, carcinoma, and tumor. All searches were performed by reviewing articles and abstracts cited in the published systematic reviews and case-control studies. Prospective studies that reported relative risk (RR) estimates with 95% CIs for the association between HPV and EC were included.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information files.
Thirty-three randomized studies were identified, and the main features of these trials were
included in this systematic review. HPV infection rate in the EC group was 46.5%, while
HPV infection rate in the control group was 26.2% (OR = 1.62; 95% CI, 1.33–1.98). In
China, the merger OR value was 1.62 (95% CI: 1.26–2.07); while in the Asian region, the
merger OR value was 1.63 (95% CI: 1.29–2.04). There were statistical differences in HPV
testing due to different detection methods such as PCR, IHC and ISH. In the PCR detection
group, the merger OR value was 1.61 (95% CI: 1.33–1.95).
These results indicate that HPV infection and the incidence of EC are closely associated.
Competing Interests: The authors have declared
that no competing interests exist.
Abbreviations: HPV, human papillomavirus; EC,
esophageal carcinoma; RR, risk ratio; CIs,
confidence intervals; PCR, polymerase chain
reaction; ISH, in situ hybridization; ICH,
immunohistochemistry; ELISA, enzyme-linked
immunosorbent assay; FEM, fixed effects model;
REM, random effects model; OR, odds ratio; EBV,
Esophageal carcinoma (EC) is the most aggressive malignant tumor of the gastrointestinal
tract and the eighth most commonly occurring cancer in the world [
]. It has been well
recognized that the development of EC involves multiple factors in a multistage process [
tobacco, nutritional deficiencies, infectious agents, etc. were confirmed to have a relationship
to esophageal carcinogenesis [
]. However, many physical, chemical and biological factors
related to EC remain unknown.
Human papillomavirus (HPV) infections, especially high-risk types 16 and 18, have recently
been reported as a possible risk factor for EC. However, direct evidence of this relationship has
been lacking, and results of those studies were not consistent. This study aimed to conduct a
meta-analysis, and systematic review of literature to determine whether an association exists
between HPV type 16 and 18 infection and EC.
Materials and Methods
A literature search was performed from 1982 to 2014 using PUBMED and CNKI databases
without restrictions, and the following search terms were used: (human papillomavirus, HPV)
and (esophageal, esophagus) and (cancer, carcinoma, tumor). Moreover, reference lists were
reviewed to search for relevant studies. This systematic review was planned and reported in
adherence to the standards of quality for reporting systematic reviews.
Inclusion and Validity Criteria
All searches were performed by reviewing articles and abstracts cited in the published
systematic reviews and case-control studies. Inclusion criteria were as follows: (1) prospective
casecontrol studies, (2) EC diagnosed by pathology, (3) Control group obtained from esophageal
epithelial tissues of normal individuals (screening) or normal marginal tissues of EC.
Exclusion criteria included the following: reports of poor quality, duplicate reports, inadequate
information, unclear data descriptions or samples were removed, sample size less than 20, and
The Jadad scoring method was used to evaluate several aspects of the quality of the study.
Three independent researchers extracted data, blindly evaluated the quality of the literature,
and analyzed the data including withdrawals and dropouts [
]. If there were differences of
opinion, the cases were discussed until consensus was achieved.
A heterogeneity test was used to select the method of data combination in the systematic
review. The Cochrane’s Q-test was performed and I2 statistics were obtained, using a
predefined significance threshold of 0.05.If P 0.05, it was considered that there was no
heterogeneity between studies; and a fixed effects model (FEM) was used for the analysis. If P<0.05, it was
considered that heterogeneity existed between studies; and a random effects model (REM) was
used after correction for analysis. If a null hypothesis, which represents that there was no
heterogeneity among each study, was accepted, the Mantel-Haenszel fixed-effects model was used
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to calculate the combined odds ratio (OR) with 95% confidence intervals (CI) and the Forest
Plot. If the null hypothesis was rejected, REM was used to calculate the combined OR with 95%
CI and the Forest Plot. To detect publication bias, the asymmetry of standard error–based
funnel plots was examined using the linear regression method, as suggested by Egger et al. [
Stata10.0 software (Stata Corporation, College Station, Texas) was used for the statistical
analysis in this study.
EC incidence in subgroups were stratified and analyzed according to various geographical
areas, the control group selection method, and various HPV detection methods.
A total of 297 articles were identified by using the search criteria, and these studies were carried
out from 1982 to 2014. All studies were obtained from published literature (Fig 1). Nine
countries including China, Iran, Italy, Greece, Egypt, Sweden, Japan, France and Mexico were
involved in the case-control studies. A total of 33 case-control studies were selected for analysis.
There was no statistical significance in factors such as gender or age between the two groups.
The PRISMA checklist is shown in S1 PRISMA Checklist.
Information of articles
Detailed steps of the literature search are shown in Fig 1. The inclusion and exclusion of
case-control studies for this systematic review are shown in the flow chart. Briefly, 33 articles matched the
]. Among the 2,430 cases in the EC group, 1,131 were HPV positive (46.54%);
Fig 1. Selection of studies for inclusion in the meta-analysis.
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Lower: lower incidence of esophageal carcinoma (EC); Higher: higher incidence of EC; PCR: polymerase chain reaction; IHC: immunohistochemistry; ISH:
in situ hybridization; ELISA: enzyme-linked immunosorbent assay. Adjacent-normal: the control group was obtained from the normal marginal tissue of EC
during surgery. True-normal: controls were obtained from the normal esophageal epithelial tissue.
while among the 3,621 cases in the control group, 977 were HPV positive (26.98%). In the control
group, 14 samples came from adjacent normal tissues of gastrointestinal cancers, while 19 samples
came from normal esophageal specimens. These samples were obtained during the esophageal
cancer screening of healthy people living in areas of high incidence of esophageal cancer (Table 1).
Thirty-three tests for heterogeneity (i = 94.78, P<0.001) revealed that there was heterogeneity
between studies and between subgroups. Therefore, overall and subgroup analyses were
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PCR: polymerase chain reaction; IHC: immunohistochemistry; ELISA: enzyme-linked immunosorbent assay; ISH: in situ hybridization; REM: random effects
model; OR: odds ratio; CI: confidence interval.
corrected using REM; and the method of DerSimonian-Laird as used to merge data, and
calculate ORs and 95% CIs. Egger’s regression analysis was used to more objectively evaluate
publication bias (Table 2).
The relationship of HPV types 16 and 18 and EC
Among the 33 studies, infection rate in the EC group was 46.5%, while infection rate in the
control group was 27.0%. Heterogeneity test revealed that there was heterogeneity (χ2 = 78.4,
P<0.001) with a P<0.05 for the Q-test. A REM analysis was applied. The combined effect of
these test results revealed an association between HPV infection and EC. From the
independent OR and synthetic OR of the 33 researches, HPV infection was found to be closely
associated with EC. The merger OR value was 1.62; 95% CI of 1.33–1.981.57, Fig 2. The accuracy of
each study as argument, with OR/SE as the dependent variable, had a 95% CI of -0.0111784–
2.63736 (P = 0.058). Therefore, there was no significant bias in the publications, there was no
substantive effect on the synthetic OR, and the conclusion was reliable (Fig 3).
Subgroup systematic review
EC incidence in subgroups were stratified and analyzed according to various geographical
areas (Fig 4A–4C), the control group selection method (Fig 5), and various HPV detection
There were 21 case-control studies in China. The merger OR value was 1.62 (95% CI: 1.26–
2.07) including high incidence areas for EC such as the Taihang, Qinling and Dabie mountain
ranges, as well as the northeast of Sichuan, east of Xinjiang, east of Fujian and east of
Guangdong provinces. No publication bias (Egger’s test, P>0.05) was found, indicating that the
results had good reliability. In other regions (outside China) such as Egypt, France, Greece,
Iran and other countries, merger OR value was 1.80 (95% CI: 1.16–2.79); and there was also no
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Fig 2. Individual trial and overall risk ratios of the association between HPV (types 16 and 18) infection and esophageal carcinoma.
publication bias (Egger’s test, P>0.05). In Asian countries such as China, Japan and India, the
merger OR value was 1.63 (95% CI: 1.29–2.04); and there was no publication bias (Egger’s test,
P>0.05). In non-Asian countries such as Egypt, France, Greece, Iran, Italy, Mexico and
Sweden, merger OR value was 1.64 (95% CI: 1.01–2.67); and there was no publication bias (Egger’s
test, P>0.05). In addition, results were same in both high risk and low risk areas. In high risk
areas, merger OR value was 1.29 (95% CI: 1.05–1.59); while in low risk areas, merger OR value
was 2.06 (95% CI: 1.08–3.94). (Fig 4A–4C)
In the control patient group (healthy individuals), merger OR value was 1.41 (95% CI: 1.06–
1.89); while in the control tissue group (normal tissues from EC patients), merger OR value
was 1.82 (95% CI: 1.36–2.42, Fig 5).
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Fig 3. Begg’s funnel plot on studies of HPV infection and esophageal carcinoma.
Various HPV detection methods were summarized and analyzed: 18 cases were detected by
PCR, 6 cases were detected by ISH, 6 cases were detected by IHC, and 3 cases were detected by
ELISA. In the PCR group, merger OR value was 1.61 (95% CI: 1.33–1.95); in the ISH group,
merger OR value was 1.21 (95% CI: 0.62–2.36); and in the IHC group, merger OR value was
1.69 (95% CI: 0.96–2.96). An opposite result was acquired in the ELISA group, where the
merger OR value was 1.28 (95% CI: 0.54–3.04; Fig 6A–6D).
EC is the fifth most common cancer in developing countries, and the eighth most common
]. Areas of high prevalence for EC are mainly located in developing
countries, and there are obvious regional differences. [
] The world’s highest areas of incidence are
located in Asia, which is called, the "EC belt" [
]. ECs vary greatly by geographic distribution,
in which there is a higher incidence in China, America and the eastern Himalayas [
However, the incidence of esophageal cancer is low in developed Western countries.
There are several proposed risk factors for EC including eating habits, tobacco, alcohol,
pollution, genetic factors, infection of HPV viruses and EBV (Epstein-Barr) virus [
history (immediate blood relatives within three generations), etc. In developed countries, tobacco
and alcohol is a major factor [
]. However, it is different in countries with high incidence
of EC, as few cases are attributed to smoking or alcohol consumption there [
Currently, the role of HPV infection in esophageal cancer is unclear. Many studies from
Africa and China have shown that HPV infections were associated with esophageal cancer.
However, in areas with lower prevalence of HPV, there was no decrease in risk of EC [
The differences in the results of the studies may be due to: 1. Differences in race, living habits,
environmental factors that lead to HPV infection. 2. Differences in research design, detection
means, methods, statistical analysis. The aim of this study was to perform a comprehensive
analysis of the data to determine the relationship between EC and HPV.
In order to explain the association between HPV and EC, we reviewed many articles and selected
only case-control studies for analysis. To our knowledge, this is the first study that conducted a
systematic review of the relationship between HPV infection (types 16 and 18) and EC worldwide.
Results of the comprehensive evaluation of this final systematic review revealed that there was a
significant association between HPV infection and EC risk with an integrated OR = 1.62 (95% CI:
1.33–1.98). In META analysis, the presence or absence of heterogeneity directly affected the results
of the statistics. Therefore, this study was conducted to strictly evaluate heterogeneity.
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Fig 4. Individual trial and overall risk ratios of relationships between HPV infection and esophageal carcinoma in various geographical
areas. 4A: China, 4B: non-China and 4C: Asia/non-Asia.
HPV infection rates may be related to geographical location. Therefore, we preformed a
subgroup analysis according to geographical location worldwide. The stratification study
revealed that regardless of whether the studies were in China, Asia, outside of China, or outside
of Asia, or in high or low risk areas, HPV infection was associated with EC. In the current
research, most studies from low-risk areas also had an association between HPV and EC, and
these correlations were stronger than high-risk areas; which was different from other reports.
A possible reason was that in high-risk areas, EC occurred due to other reasons such as eating
habits, tobacco, alcohol, pollution, genetic factors and HPV infection; thus, the influence of
HPV decreased [
]. In low-risk areas, HPV infection appears to be the main cause.
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Fig 5. Individual trial and overall risk ratios of relationships between HPV infection and esophageal
carcinoma compared to various controls.
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Fig 6. Individual Trial and Overall Risk Ratios of Relationships between HPV Infection and EC using Various Detection Methods. (6A:PCR,
6B IHC, 6C:ISH, 6D:ELISA).
Although most of the esophageal cancer risk factors have been determined, there may still
be unknown confounders that may interfere with the results. The literature included
case-control studies that were inevitably affected by a variety of bias.
However, due to the current study design, many kinds of bias were possible. (1) Most
studies detected HPV from tumor tissues and tissues around tumors that could have been infected
with HPV. (2) This systematic review included many studies from all over the world. The
variable HPV prevalence could have been related to the various geographic regions studied.
The choice of the control group may have also affected the results, because the healthy
controls group revealed that HPV was associated more closely with EC. Cancer adjacent tissues as
controls also confirmed a link between HPV and EC, but with a weaker correlation than the
cancer tissue itself. This may be related to the HPV infection of the cancer tissue in the body or
contamination of samples. There are many methods for detecting HPV, and there was no
uniform detection method used in these studies. The researchers did not make use the same HPV
detection methods used such as PCR, ELISA, ISH and IHC; although some of the early HPV
detection techniques have since been abandoned. Therefore, these results are likely to have
some bias, and PCR seems to be the most accurate monitoring method [
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The current result was the same as that reported by Zhang et al. [
] except that their
study was limited to a Chinese population, and used a PCR detection method for HPV16.
Zhang et al. found that there was a relatively high level of HPV 16 prevalence in Chinese
patients with esophageal cancer, and concluded that HPV-16 infection may be a risk factor for
esophageal cancer. The current research included the entire world population, and all methods
to detect HPV16. Using a subgroup analysis, we obtained results similar to those of Zhang
et al. While, there was the limitation that the analyses did not distinguish between the two
primary histologic forms of esophageal cancer: squamous cell carcinoma and adenocarcinoma.
From our research, squamous cell carcinoma were more likely linked to HPV, adenocarcinoma
was fewer than squamous cell carcinoma. This may be related to its biological characteristics.
These results indicate that HPV is closely associated with EC in China, Asia, and all over the
world. In investigating the association between HPV and EC, the selection of the control group
is important in order to avoid interfering factors. This systematic review provides
epidemiologic evidence to support the association between HPV infection and EC. Multi-center studies
on regional incidences with strict control of false positives and false negatives would be needed
to confirm the association of HPV and EC. If confirmed, HPV testing may be useful in groups
at high risk for EC; while HPV vaccine might be useful as a primary prevention measure.
Guarantor of the article: Bangwei Cao, PhD and Bing Liu
S1 PRISMA Checklist. The PRISMA checklist.
Conceived and designed the experiments: JW BC BL. Performed the experiments: LZ LH JC
WJ. Analyzed the data: HY. Contributed reagents/materials/analysis tools: BC BL. Wrote the
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