Year-on-year analysis of the number of papers published worldwide using PDX (A), the proportion of those papers that used PDX and were associated with clinical trials (B), and the number of papers published using PDO (C). The number of studies using PDX, for all three types of cancer, shows some fluctuations but overall remain the same over the time period evaluated (A). Likewise, there is no growing trend for the number of publications using PDX and associated with clinical trials between 2014 and 2019 (B)—these data are expressed as the number of studies associated with a clinical trial relative to the total number of publications using PDX. However, panel C shows that the number of published studies using PDO increase over time but note that the total number of papers is still low compared to the number of studies using PDX (panel A).