Forest plot of OS data. Plot shows meta-analysis result of all assessed studies reporting OS. Subgroup analysis according to the sample origin is also shown. Blue squares indicate the relative weight of each study in the meta-analysis and horizontal lines represent the 95% CI for the effect size. Larger squares show studies with higher relative weights. Weights are from random-effects analysis and are based on the size of the study and the number of events. Red diamonds represent the total effect size. IV, inverse variance. SE, standard error.