(a) EGFR for bladder cancer progression
(b) ErbB2 for bladder cancer death
Figure 3: Funnel plots of publication bias for EGFR and ErbB2. (a) No obvious funnel plot asymmetry was found for EGFR because only four studies were analyzed. (b) A substantial funnel plot asymmetry for ErbB2 was found, which suggests the existence of publication bias.