Figure 4 The grey zone between active surveillance (AS) and watchful waiting based on expert consensus Figure 4 | The grey zone between active surveillance (AS) and watchful waiting based on expert consensus. This grey zone was described by the experts as a phase of active (regular) annual monitoring of serum PSA levels (no biopsies undertaken) with the aim of palliation when deemed necessary. Bruinsma, S. M. et al. (2017) Semantics in active surveillance for men with localized prostate cancer — results of a modified Delphi consensus procedure Nat. Rev. Urol. doi:10.1038/nrurol.2017.26