Study selection and description of the include studies
A total of 2106 articles were obtained through database search. After removing duplicated studies and irrelevant studies through screening title and abstract, 40 studies were remained. Then, the full texts of the articles were reviewed in detail, and 10 studies met our inclusion criteria were finally included for the meta-analysis, including 4 studies detecting FBXW7 mutation and 6 studies measuring FBXW7 expression. The main characteristics of the included studies are presented in Table 1. These studies were published between 2009 and 2019, and conducted in 4 countries (China, Australia, America, and Japan). The overall sample size was 4199, ranging from 50 to 1519. The relationship between OS and FXBW7 status was all described in the 10 studies, and DFS was reported in 4 studies. All of the eligible entries scored more than five by NOS, revealing a high methodological quality across all studies. FBXW7 expression was measured by IHC or qRT-PCR, and mutation was detected though different sequencing methods. For the purposes of this anlaysis, cases with low expression of FBXW7 or coding mutations were considered one similar group of patients that had tumors with a deficit in FBXW7.
Correlation between FBXW7 and clinicopathological features
Correlation between FBXW7 status and clinicopathological features was presented in 8 studies. Based on the ORs derived from these studies, we evaluated the correlation between FBXW7 status and some clinicopathological characteristics, including age, gender, histological grade, tumor size, tumor location, venous invasion, peritoneal metastasis, depth of invasion, lymph node metastasis, distant metastasis, TNM stage and Duke’s stage.(Table 2) Aberrant FBXW7 status was significantly associated with advanced T stage (OR = 0.44, 95% CI: 0.27–0.74, P < 0.01) and lymph node metastasis (OR = 1.88, 95% CI: 1.40–2.53, P < 0.01). Frequency of venous invasion was also higher in FBXW7 mutation/low expression cohort, but no statistical significance was detected (OR = 1.63, 95% CI: 1.01–2.64, P = 0.05). No obvious relationship was verified between FBXW7 status and other parameters. (Table 2)
Prognostic value of FBXW7
All the 10 studies were enrolled to detect the prognostic value of FBXW7 in OS. A random-effect model was used to calculate the pooled HR and 95% CI because excessive heterogeneity existed between studies (P < 0.01, I2=73%). (Fig. 2A) Overall, FBXW7 mutation/low expression predicted poor OS (HR = 1.25, 95% CI: 1.06–1.47, P < 0.01). (Fig. 2A) However, no significant correlation was found between FBXW7 and DFS in CRC (HR = 1.04, 95% CI: 0.60–1.82, P = 0.88). (Fig. 2B) To detect potential heterogeneity, subgroup analyses were stratified based on recruitment time, region, FBXW7 detection method, sample size and data type to evaluate FXBW7 prognostic value in CRC. As shown in Table 3, FBXW7 mutation/low expression predicted decreased OS regardless of sample size ≥ 100 (HR = 1.23, 95% CI: 1.01–1.51, P = 0.04) or < 100 (HR = 1.33, 95% CI: 1.09–1.63, P < 0.01). Besides, FBXW7 status was obviously correlated with OS in cohorts recruited after 2009 (HR = 1.32, 95% CI: 1.17–1.50, P < 0.01), from eastern Asia (HR = 1.27, 95% CI: 1.04–1.55, P = 0.02), detected by IHC/qRT-PCR (HR = 1.39, 95% CI: 1.22–1.59, P < 0.01), and analysed with multivariate method (HR = 1.47, 95% CI: 1.25–1.74, P < 0.01). However, no prognostic effect was observed in patients recruited before 2009 (HR = 1.24, 95% CI: 0.93–1.65, P = 0.14), from regions beyond eastern Asia (HR = 1.18, 95% CI: 0.87–1.61, P = 0.28), detected by sequencing (HR = 1.17, 95% CI: 0.94–1.47, P = 0.16), and analysed with univariate method (HR = 1.13, 95% CI: 0.94–1.35, P = 0.20). (Table 3)
Publication bias and sensitivity analysis
A funnel plot, with regard to the publication bias of all studies for OS and four studies for DFS, showed the basic symmetrical. (Fig. 3A and 3B) Evaluation of publication bias using Begg’s and Egger’s tests also showed that no publication bias existed (P value of Begg’s test, 0.24 and 0.31 for OS and DFS, respectively; P value of Egger’s test, 0.75 and 0.08 for OS and DFS, respectively). Furthermore, to evaluate the results of meta-analysis, sensitivity analysis was conducted. No significant change was found in the results when any 1 study was excluded, confirming the robustness and reliability of meta-analysis results on both OS and DFS (Table 4).