Fig. 2

Patient registration rate for the 55 participating centers individually. Each dot represents one individual participating center. The dashed, horizontal line represents the median registration rate (85.7%). The dashed, vertical lines represent the cut-off values applied for making a distinction between low- (< 10 cases/year), medium- (10–19 cases/year), and high-volume (≥ 20 cases/year) centers. A center's registration rate was calculated as the percentage of patients that were registered for EFFECT by that specific hospital (REP) out of the total number of patients that underwent their main treatment during the active registration period of that particular hospital (REP + non-REP). Min = minimum; max = maximum; Q1 = first quartile; Q3 = third quartile