A word of caution on using tumor biomarker reference change values to guide medical decisions and the need for alternatives.

Keywords: evidence based-medicine; reference change value; tumor biomarker EN evidence based-medicine reference change value tumor biomarker 553 555 3 03/11/22 20220301 NES 220301 To the Editor, A word of caution on using biomarker reference change values (RCV) to guide medical decisions: In a recent study from the EFLM working group on biological variation, the biological variation of tumor markers has been investigated and estimates of the within and between subject biological variations were obtained [[1]]. Also, cancer treatment itself has a significant effect on the tumor and therefore tumor biomarker dynamics. [Extracted from the article]