1. Radiotherapeutic Institute Limburg, Heerlen, The Netherlands
2. Department of Surgery, Academic Hospital Maastricht, Maastricht, The Netherlands
3. Department of Pathology, Academic Hospital Maastricht, Maastricht, The Netherlands
4. Cancer Registry, Comprehensive Cancer Centre Limburg, Maastricht, The Netherlands
5. Department of Methodology and Statistics, University of Limburg, Maastricht, The Netherlands