Indian Journal of Cancer
Home  ICS  Feedback Subscribe Top cited articles Login 
Users Online :183
Small font sizeDefault font sizeIncrease font size
Navigate here
  Search
 
  
Resource links
 »  Similar in PUBMED
 »  Search Pubmed for
 »  Search in Google Scholar for
 »Related articles
 »  Article in PDF (374 KB)
 »  Citation Manager
 »  Access Statistics
 »  Reader Comments
 »  Email Alert *
 »  Add to My List *
* Registration required (free)  

 
  In this article
 »  Abstract
 » Introduction
 »  Materials and Me...
 » Results
 » Discussion
 »  References
 »  Article Figures
 »  Article Tables

 Article Access Statistics
    Viewed393    
    Printed6    
    Emailed0    
    PDF Downloaded110    
    Comments [Add]    

Recommend this journal

 


 
  Table of Contents  
ORIGINAL ARTICLE
Year : 2015  |  Volume : 52  |  Issue : 6  |  Page : 112-115
 

A meta-analysis of the association between Chlamydia pneumoniae infection and lung cancer risk


Department of Emergency, The 6th Affiliated Hospital of Wenzhou Medical University, Lishui People's Hospital 323000, Zhejiang, Lishui, China

Date of Web Publication24-Dec-2015

Correspondence Address:
D Junyi
Department of Emergency, The 6th Affiliated Hospital of Wenzhou Medical University, Lishui People's Hospital 323000, Zhejiang, Lishui, China
China
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0019-509X.172506

Get Permissions

 » Abstract 

Objective: The association between Chlamydia pneumoniae infection and lung cancer risk was not clear with small number of cases in each study. The aim of this meta-analysis was to evaluate the correlation between pneumonia infection and lung cancer risk by pooling the open published papers. Materials and Methods: We searched the electronic databases of Medline, EMBASE, Web of Science, and China National Knowledge Infrastructure databases for publications related to the association between pneumonia infection and lung cancer risk. Odds ratio (OR) and its 95% confidence interval (95% CI) was used to assess the correlation. The data were pooled by Stata11.0 software (Stata Corporation, College Station, TX, USA). Results: Thirteen publications, involving 2549 lung cancer patients and 2764 controls were included in this meta-analysis. The pooled results indicated that the C. pneumoniae infection significant increased the risk of lung cancer OR = 2.07 (95% CI: 1.43–2.99) by random effect model. And for serum IgG, 12 publications reported the IgG positive rate in lung cancer patients and relative healthy controls. The pooled OR was 2.22 (95% CI: 1.41–3.50) by using the random effects model which indicated that the IgG positive rate was significantly higher in lung cancer patients than that of healthy controls. The sensitivity analysis indicated the pooled OR was not sensitive to a single study. However, Begger's funnel plot and Egger's line regression analysis indicated significant publications bias for this meta-analysis. Conclusions: According to the present published data, C. pneumoniae infection may increase the risk of lung cancer. However, for its significant publications and heterogeneity among the included studies, the conclusion should be interpreted cautiously.


Keywords: Chlamydia pneumoniae infection, lung cancer, meta-analysis, risk factors


How to cite this article:
Hua-Feng X, Yue-Ming W, Hong L, Junyi D. A meta-analysis of the association between Chlamydia pneumoniae infection and lung cancer risk. Indian J Cancer 2015;52, Suppl S2:112-5

How to cite this URL:
Hua-Feng X, Yue-Ming W, Hong L, Junyi D. A meta-analysis of the association between Chlamydia pneumoniae infection and lung cancer risk. Indian J Cancer [serial online] 2015 [cited 2016 Jul 24];52, Suppl S2:112-5. Available from: http://www.indianjcancer.com/text.asp?2015/52/6/112/172506



 » Introduction Top


As we all known, lung cancer is the leading cause of cancer-related death word wide.[1] It was estimated that

1.4 million deaths related to lung cancer were found in the year 2008.[2] Although the diagnostic and treatment method was developed in the recent 10 years, the morbidity and mortality rate was still on the rise. The mechanism of lung cancer was not fully understood. However, several risk factors for lung cancer was confirmed by experiment or epidemiology study. Smoking status was confirmed as the independent risk factor for developing lung cancer.[3],[4] Moreover, other carcinogenesis for lung cancer was also found such as radon and asbestos exposure, air pollution, second-hand smoking, genetic susceptibility, and chronic bacterial infection. Recently, several studies have evaluated the Chlamydia pneumoniae infection and lung cancer risk.[5],[6] However, for the small number subjects of each study, the results were not conclusive. Thus, we perform this meta-analysis using open published studies to further assess the relationship between C. pneumoniae infection and lung cancer risk.


 » Materials and Methods Top


Search strategy

We searched the electronic databases of Medline, EMBSE, Web of Science, and China National Knowledge Infrastructure (CNKI) databases for publications related to the association between pneumonia infection and lung cancer risk. The search terms were “lung cancer/carcinoma of the lung” and “C. pneumoniae.” The study objects were limited to human beings, with the language restriction of English and Chinese. All potential relevant studies were assessed in detail, and additional all citations of the included articles were further evaluated in order to identify additional suitable studies. The inclusion criteria were: (1) Study design was limited to prospective cohort study or retrospective case–control study; (2) the patients were pathology clinical confirmed lung cancer; (3) the controls were relative healthy people with no diagnosis of any cancer; (4) the C. pneumoniae infection rate can be extracted from the included individual study. The data were extracted by two reviewers (Xu Hua-Feng, Wu Yue-Ming) independently from all included studies. The year of publication, the first author name, the study design, and the positive number of C. pneumoniae infection were extracted from the included studies.

Statistical analysis

Stata/SE 11.0 (Stata Corporation, College Station, TX, USA) software was used to deal with the data analysis. The odds ratio (OR) was calculated for evaluated the correlation between C. pneumoniae infection and lung cancer risk. The heterogeneity among the included 13 publications was assessed by Chi-square test. The DerSimonian-Laird random effects method for pooling the OR was used if significant heterogeneity was found. Otherwise, the fixed effect model was applied. The publication bias was detected by funnel plot and Egger's line regression test.[7]


 » Results Top


Main characteristics of the included 13 publications

We searched the electronic databases of Medline, EMBSE, Web of Science, and CNKI databases for publications to include in this meta-analysis. Finally, 13 publications involving 2549 lung cancer patients and 2764 controls were included in this meta-analysis. For the included 13 studies, 4 studies were published in Chinese, and other 9 papers were published in English. For the study design, 4 papers are nest case–control, and other 9 are case–control studies. The serum IgA positive rate for C. pneumoniae infection rate ranges from 25.9% to 86.3% for the lung cancer groups and 6.8% to 71.2% for the healthy control group. The main characteristics of included publications are showed in [Table 1].
Table 1: The main characteristics of the included 13 publications

Click here to view


Results from the meta-analysis

Twelve studies reported the association between C. pneumoniae infection and lung cancer risk by using the serum IgA. The pooled results indicated that the C. pneumoniae infection significant increased the risk of lung cancer OR = 2.07 (95% confidence interval [CI]:

1.43–2.99) [Figure 1] by random effect model. And for serum IgG, 12 publications reported the IgG positive rate in lung cancer patients and relative healthy controls. The pooled OR was 2.22 (95% CI: 1.41–3.50) [Figure 1] by using the random effects model, which indicated that the IgG positive rate was significantly higher in lung cancer patients than that of healthy controls. These results demonstrated that C. pneumoniae infection was significantly correlated with the lung cancer.
Figure 1: Forest plot for association between chlamydia pneumoniae infection and lung cancer risk

Click here to view


Sensitivity analysis

A single publication involved in the meta-analysis was omitting each time to reflect the influence of the individual data set to the pooled ORs. The OR ranged from 1.20 (95% CI: 1.13–1.28) to 1.31 (95% CI: 1.22–1.40) for IgA [Figure 2] and 1.09 (95% CI: 1.05–1.46) to 1.19 (95% CI: 1.14–1.25) for IgG [Figure 3] with only a slight change. The sensitivity analysis indicated the pooled OR was not sensitive to a single study, which demonstrated that the results were relative stable.
Figure 2: Forest plot for sensitivity analysis of IgA

Click here to view
Figure 3: Forest plot for sensitivity analysis of IgG

Click here to view


Publication bias

Begger's funnel plot and Egger's line regression tests were used to evaluate the publication bias of this meta-analysis.[7] The Begger's funnel plot [Figure 4] and [Figure 5] showed obvious asymmetry. Moreover, Egger's line regression test also indicated significant publication bias (P < 0.05).
Figure 4: The funnel plot of publication bias for IgA

Click here to view
Figure 5: The funnel plot of publication bias for IgG

Click here to view



 » Discussion Top


Lung cancer is still the deadliest cancer worldwide despite improvements in diagnostic and therapeutic techniques for the recent several years. Moreover, full understanding of carcinogenesis for lung cancer was not reached. The independent risk factor for lung cancer is smoking which has been confirm by several experiment studies or epidemiology studies in the past several decades.[18] However, other risk factors such as bacterial infection, radon exposure, and genetic susceptibility were not absolutely confirmed.

In 1997, Laurila et al.[17] first hypothesized that C. pneumoniae might correlate with increased risk of lung cancer based on an observation case–control study. Thereafter, several studies were conducted to further evaluate the association between C. pneumoniae infection and lung cancer risk. However, for weak statistical power, the results have been inconsistent. Meta-analysis is a powerful tool for studying cumulative data from individual studies with small sample sizes and low statistical power.[19] Pooling the effects from individual studies by a meta-analysis may increase the statistical power and can help detect modest risk differences among study groups. Thus, we perform this meta-analysis through pooling the publication data. In our meta-analysis, we finally included 13 articles with 4 published in Chinese and 9 published in English. The pooled results showed that the C. pneumoniae infection significant increased the risk of lung cancer OR = 2.07 by random effect model for IgA. And for serum IgG, the pooled OR was 2.22 (95% CI: 1.41–3.50) by using the random effects model which indicated that the IgG positive rate was significant higher in lung cancer patients than that of healthy controls. Both using the IgA and IgG as the C. pneumoniae infection diagnosis method, the significance for infection and lung cancer risk was observed.

We also conducted the sensitivity analysis by deleting each individual study to further assess the OR. We found that the pooled OR was not sensitive to a single study which indicated the result was stable. However, the publication analysis indicated significant publication bias by Begger's funnel plot and Egger's line regression analysis. Hence, we believe that according to the present published data, C. pneumoniae infection may increase the risk of lung cancer. However, for its significant publications bias and heterogeneity among the included studies, the conclusion should be interpreted cautiously.

 
 » References Top

1.
Siegel R, Naishadham D, Jemal A. Cancer statistics, 2012. CA Cancer J Clin 2012;62:10-29.  Back to cited text no. 1
    
2.
Jemal A, Bray F, Center MM, Ferlay J, Ward E, Forman D. Global cancer statistics. CA Cancer J Clin 2011;61:69-90.  Back to cited text no. 2
    
3.
Islami F, Torre LA, Jemal A. Global trends of lung cancer mortality and smoking prevalence. Transl Lung Cancer Res 2015;4:327-38.  Back to cited text no. 3
    
4.
Ou SH. Lung cancer in never-smokers. Does smoking history matter in the era of molecular diagnostics and targeted therapy? J Clin Pathol 2013;66:839-46.  Back to cited text no. 4
    
5.
Fei H, Lin C. Association between Chlamydia pneumonia infection and lung cancer risk. Chin J Public Health 2014;12:70-3.  Back to cited text no. 5
    
6.
Anttila T, Koskela P, Leinonen M, Laukkanen P, Hakulinen T, Lehtinen M, et al. Chlamydia pneumoniae infection and the risk of female early-onset lung cancer. Int J Cancer 2003;107:681-2.  Back to cited text no. 6
    
7.
Egger M, Davey Smith G, Schneider M, Minder C. Bias in meta-analysis detected by a simple, graphical test. BMJ 1997;315:629-34.  Back to cited text no. 7
    
8.
Chaturvedi AK, Gaydos CA, Agreda P, Holden JP, Chatterjee N, Goedert JJ, et al. Chlamydia pneumoniae infection and risk for lung cancer. Cancer Epidemiol Biomarkers Prev 2010;19:1498-505.  Back to cited text no. 8
    
9.
Smith JS, Kumlin U, Nyberg F, Fortes C, Zaridze D, Ahrens W, et al. Lack of association between serum antibodies of Chlamydia pneumoniae infection and the risk of lung cancer. Int J Cancer 2008;123:2469-71.  Back to cited text no. 9
    
10.
Chen YB, Tao YD, Ling CH, Lin W. The association between Chlamydia pneumoniae infection and lung cancer risk. Chin J Public Health 2014;17:69-72.  Back to cited text no. 10
    
11.
Koh WP, Chow VT, Phoon MC, Ramachandran N, Seow A. Lack of association between chronic Chlamydophila pneumoniae infection and lung cancer among nonsmoking Chinese women in Singapore. Int J Cancer 2005;114:502-4.  Back to cited text no. 11
    
12.
Littman AJ, White E, Jackson LA, Thornquist MD, Gaydos CA, Goodman GE, et al. Chlamydia pneumoniae infection and risk of lung cancer. Cancer Epidemiol Biomarkers Prev 2004;13:1624-30.  Back to cited text no. 12
    
13.
Chen YQ, Li LM, Wang FC. The research of Chlamydia pneumoniae infection in patients with lung cancer. Chin J Zoonoses 2001;17:46-9.  Back to cited text no. 13
    
14.
Koyi H, Brandén E, Gnarpe J, Gnarpe H, Steen B. An association between chronic infection with Chlamydia pneumoniae and lung cancer. A prospective 2-year study. APMIS 2001;109:572-80.  Back to cited text no. 14
    
15.
Xiong ZY, Chen WS, Li TQ, et al. Comparison of Mycoplasma pneumoniae infection in patients with lung cancer and chronic obstructive pulmonary disease. J West China Univ Med Sci 2000;31:124-5.  Back to cited text no. 15
    
16.
Jackson LA, Wang SP, Nazar-Stewart V, Grayston JT, Vaughan TL. Association of Chlamydia pneumoniae immunoglobulin A seropositivity and risk of lung cancer. Cancer Epidemiol Biomarkers Prev 2000;9:1263-6.  Back to cited text no. 16
    
17.
Laurila AL, Anttila T, Läärä E, Bloigu A, Virtamo J, Albanes D, et al. Serological evidence of an association between Chlamydia pneumoniae infection and lung cancer. Int J Cancer 1997;74:31-4.  Back to cited text no. 17
    
18.
Schmidt-Hansen M, Page R, Hasler E. The effect of preoperative smoking cessation or preoperative pulmonary rehabilitation on outcomes after lung cancer surgery: A systematic review. Clin Lung Cancer 2013;14:96-102.  Back to cited text no. 18
    
19.
Anwar S. Evidence based medicine, systematic reviews and meta-analysis of literature: A powerful tool for the practising doctor. J Coll Physicians Surg Pak 2007;17:123-4.  Back to cited text no. 19
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
 
 
    Tables

  [Table 1]



 

Top
Print this article  Email this article
 

    

  Site Map | What's new | Copyright and Disclaimer
  Online since 1st April '07
  © 2007 - Indian Journal of Cancer | Published by Wolters Kluwer - Medknow