Cancer Genetics and Epigenetics 2019, Vol.7, No.1, 1-10
7
3 Materials and Methods
All analyses were based on previous published studies, thus no ethical approvals or patient consents were required.
This recommended Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines is adhered to
the meta-analysis (Moher et al., 2009).
3.1 Inclusion criteria
Case-control studies which should met the following eligibility criteria were included: (1) polymerase chain
reaction (PCR) which include PCR-polymerase chain reaction-single strand conformation polymorphism (SSCP)
and PCR-polymerase chain reaction restriction fragment length polymorphism (RFLP) for genotyping were used
to genotype; (2) The relation in the TP53 codon 72 polymorphism and NPC susceptibility is evaluated; (3)
enabled the genotypes to be computed from the available publications, or the number of the persons genotypes in
both the case and control groups were provided; (4) NPC patient who were diagnosed by obviously reported the
type or, histologic methods and cancer-free controls or contained healthy were included; (5) the publications
should be published in Chinese or English.
3.2 Search strategy
Some databases were searched up to March 2015, which include EMBASE, MEDLINE, AMED, EBM, ACP,
Health Technology Assessment, NHS, CNKI and so on. And we searched the following items: [(nasopharyngeal)
AND (cancer OR carcinoma) AND (p53 OR TP53) AND polymorphism]. Additionally, we screened for
additional studies which included published studies on interrelated topics and the included studies reference lists.
3.3 Data extraction
The following trial data which was extracted from included studies was extracted by two authors independently:
the year of publication, the names of the authors, the countries of the publication, the NPC diagnostic method, the
method of genotyping, source of control, cases and controls numbers and the genotyping distributions, and the
controls Hardy-Weinberg Equilibrium (HWE) (Salanti et al., 2005). If there were disagreements, we should
discuss to resolve them.
3.4 Statistical analysis
The Chi-square test (χ2; heterogeneous was p<0.10) and the inconsistency index test (I; indicate higher
heterogeneity shows larger I values) evaluated assessment of heterogeneity. Any significant heterogeneity selected
to solve the random effects model in the studies. If not, it should use the fixed-effects model (Mantel-Haenszel)
(Moher et al., 2009). Publication bias was used to evaluate the Egger regression asymmetry test (Salanti et al.,
2005) and Begg’s rank correlation test (Huedo-Medina et al., 2006) and indicative of a lack of publication bias
considered a p value of >0.05. We used STATA version 12.0 (StataCorp, Texas, USA) to perform statistical
analyses, and it was considered significant, when <0.05.
The fixed-effect analytical model first to pool results of the included studies were employed and statistical
heterogeneity was tested by I
2
statistic (Huedo-Medina et al., 2006). It should be switched to a random-effects
model, once I
2
was more than 40%. In order to quantify in the TP53 codon 72 polymorphism the strength of
relation, we used relevant 95% confidence intervals (CIs) and the odds ratios (ORs). And we used four genetic
models to assess NPC risk: ArgArg vs. (ProPro + ArgPro), (ArgPro + ArgArg) vs. ProPro, ArgPro vs. ProPro, and
ArgArg vs. ProPro. We used examination of funnel plots to detect publication bias. And Review Manager
(RevMan) software (version 5.2 for Windows) was used to conduct all statistical analyses.
4 Conclusion
In conclusion, this systematic review indicated that TP53 codon 72 polymorphisms are interrelated with NPC risk.
Homozygote Pro/Pro genotype could obviously increase risk to NPC, and Arg allele critically decreases NPC risk
at the same time.
Authors’ contributions
MCG and ZXC wrote and translated the manuscript. TZZ read and approved the final manuscript. JYD and WLJ collected materials.
All authors read and approved the final manuscript.
