The subgroup region included three variables: Europe, America, and Asia, where Europe (HR 1.86, 95% CI 1.32–2.61, P=0.000) and Asia (HR 1.83, 95% CI 1.04–3.23, P=0.037) were significantly related to worse prognosis, but not related to America (HR 1.32, 95% CI 0.98–1.79, P=0.070). The heterogeneity of America (I2=0%, Ph=0.546), Europe (I2=53.3%, Ph=0.036), and Asia (I2=85.7%, Ph=0.000) gradually increased. In the two subgroups of cutoff value and maximum follow-up time, each subitem gave significance for predicting prognosis. The heterogeneity of cutoff value <20% (I2=28.2%, Ph=0.223) and cutoff value ≥20% (I2=43.9%, Ph=0.129) was relatively low, while there was substantial heterogeneity in the subgroup of cutoff value determined by other modes and of unavailable cutoff value (I2=83.3%, Ph=0.000). There was substantial heterogeneity in the subgroup of maximum follow-up time <100 months (I2=81.8%, Ph=0.000), while there was no substantial heterogeneity in the subgroup of maximum follow-up time ≥ 100 months (I2=0%, Ph=0.976) and unavailable maximum follow-up time (I2=0%, Ph=0.944).
Prognostic significance of EGFR expression in GBM patients
GBM is one of the most common gliomas with the highest degree of malignancy. It accounts for a large proportion of the included studies, and therefore, a meta-analysis was conducted to determine the prognostic significance of EGFR expression in GBM patients. Ten studies including 1,074 patients were considered in the survival analysis. The pooled HR was 1.57 (95% CI 1.15–2.14, P=0.004, random effect; Figure 3). This indicated that high expression of EGFR was significantly associated with poor prognosis in GBM patients. Similarly, subgroup analysis was performed because of high heterogeneity (I2=83.8%, Ph=0.000). The grouping and results of subgroup analysis are displayed in Table 3.
(To view a larger version of Figure 3, click here.)
(To view a larger version of Table 3, click here.)
Sensitivity analysis and publication bias
All the studies were sequentially removed to determine whether a single study had significant influence on pooled HR and to verify the stability and reliability of HR estimates. It was found that the pooled HRs were not significantly influenced by any individual study (Figures 4 and 5).
(To view a larger version of Figure 4, click here.)
(To view a larger version of Figure 5, click here.)
Publication bias was assessed using the funnel plot (Figure 6), Begg’s and Egger’s tests. The funnel plot was asymmetrical. Begg’s test (z =0.54, P > |z| =0.592) revealed no publication bias among the 17 eligible studies, while Egger’s test (t=5.41, P > |t| =0.000) showed clear bias.