Fig. 1

Strategy of data collection and matching process. In the group of patients with diagnosis in 2014 and 2015, nationality has been examined. 255 foreign patients could be found. To enhance the possibility of finding an appropriate matching partner, the period of time in which we searched for the German matching partner was preset from 01/2010 to 06/2016 (however, we tried to ensure a concordant length of follow-up by looking for a matching partner with same year of diagnosis first). After excluding three patients due to non-validated diagnosis und 33 patients due to non-availability of a comparable matching partner, 219 foreign patients remained who could be matched to compatible German patients