1. Department of OrthopedicsLeiden University Medical Center Leiden the Netherlands
2. Leiden University Mathematical Institute Leiden the Netherlands
3. University Hospital Essen, University Duisburg. Essen Pediatrics III, Sarcoma Centre, West German Cancer Centre, German Cancer Consortium Essen Germany
4. German Cancer Consortium (DKTK) Essen Germany
5. Department of RadiotherapyLeiden University Medical Center Leiden the Netherlands
6. Department of Medical OncologyLeiden University Medical Center Leiden the Netherlands
7. Medical Statistics/Biomedical Data SciencesLeiden University Medical Center Leiden the Netherlands