Forest plots of association of circulating tumor cell (CTC) detection with disease stage. Forest plots of overall association of CTC detection with disease stage were calculated by pooling data from all assays in eligible studies (A) and by pooling data from a single detection assay per study (B). The size of each square is proportional to sample size. The center of each square and the horizontal line show the odds ratio (OR) and corresponding 95% confidence intervals (CI), respectively. The center of the diamond indicates overall OR and the ends correspond to 95%CI.