Journal of Experimental & Clinical Cancer Research 2009, 28:115 http://www.jeccr.com/content/28/1/115 6. The methods of data collection and analysis should be statistically acceptable. Accordingly, the following exclusion criteria were also used: 1. The design and the definition of the experiments were obviously different from those of the selected papers. 2. The source of cases and controls and other essential information were not offered; 3. The genetic distribution of the control group was incon- sistent with Hardy-Weinberg equilibrium (HWE). 4. Reviews and duplicated publications. After searching, we reviewed all papers in accordance with the criteria defined above for further analysis. Data extraction Data were carefully extracted from all eligible publications independently by two of the authors according to the inclusion criteria mentioned above. For conflicting evalu- ations, an agreement was reached following a discussion. If a consensus could not be reached, another author was consulted to resolve the dispute and then a final decision was made by the majority of the votes. The extracted infor- mation was entered into a database. For data not provided in the main text, the relevant information was obtained by contacting corresponding authors as possible as we could. Statistical analysis The odds ratio (OR) of TP53 codon 72 polymorphisms and breast cancer risk was estimated for each study. The pooled ORs were performed for additive model (Arg/Arg vs Pro/Pro), dominant model (Arg/Arg+Arg/Pro versus Pro/Pro) and recessive model (Arg/Arg versus Arg/ Pro+Pro/Pro), respectively. For detection of any possible sample size biases, the OR and its 95% confidence interval (CI) to each study was plotted against the number of par- ticipants respectively. A Chi-square based Q statistic test was performed to assess heterogeneity. If the result of the heterogeneity test was P > 0.05, ORs were pooled accord- ing to the fixed-effect model (Mantel-Haenszel), Other- wise, the random-effect model (DerSimonian and laird) was used. The significance of the pooled ORs was deter- mined by Z-test. The HWE was assessed via Fisher's exact test. Publication bias was assessed by visual inspection of fun- nel plots[23], in which the standard error of log (OR) of each study was plotted against its log (OR). An asymmet- ric plot indicates a possible publication bias. The symme- try of the funnel plot was further evaluated by Egger's linear regression test[24]. In addition, fail-safe number for P = 0.05 (Nfs0.05) [25] for the evaluation of the reliability of meta-analysis, defined as the number of negative results that could reverse the significant findings, was also used to estimate the robustness of the meta analysis. Sta- tistical analysis was undertaken using the program Review Manager 4.2 and SAS 8.1 software. Results Study characteristics A total of 131 studies regarding TP53 codon 72 with respect to breast cancer were searched and screened for retrieval, of which 97 irrelevant studies were excluded. Then, 9 studies [26-34] were excluded because each of them did not contain a control group. Next, of the remaining 25 studies, 2 studies[35,36] were excluded due to their insufficient data and 1 study [37] owing to its review characteristic. Afterwards, another 5 studies [38- 42] were excluded because the genetic distributions of the control groups were not in agreement with HWE. Lastly, 17 case-control studies were selected (Figure 1). Of the all included 17 studies, 16 were written in English [43-58] and 1 [59] in Chinese. We established a database according to the extracted information from each article. The relevant information was listed in Table 1. According to the lists, the first author and the number and characteristics of cases and controls for each study as well as other necessary information were presented. As shown in Table 2, the distributions of TP53 codon 72 genotype of the included studies were also pre- sented. The controls of the included studies were all in accordance with HWE. Test of heterogeneity We analyzed the heterogeneity of Arg/Arg versus Pro/Pro and dominant model (Arg/Arg+Arg/Pro versus Pro/Pro) as well as recessive model (Arg/Arg versus Arg/Pro+Pro/ Pro). As shown in Table 3, the heterogeneity for the over- all data was significant in each of the above three models respectively because the P values were less than 0.05 for Q-tests. Thus, random-effect models were utilized for the meta-analyses. Meta-analysis results Table 3 lists the main results of the meta-analysis. No evi- dence showed that individuals who carry Arg allele have an increased or decreased risk of breast carcinoma com- pared with those who carry Pro allele. In the present study, a total of 17 studies were included. Nevertheless, the study conducted by Weston et al. [44] concerned both Caucasians and Africans. Thus, the data Page 3 of 9 (page number not for citation purposes)