Leiden University Medical Center, Department of Clinical Oncology, Leiden, The Netherlands. The Netherlands Cancer Institute, Department of Statistics, Amsterdam, The Netherlands. Department of Internal Medicine, Medical Center Leeuwarden, Leeuwarden, The Netherlands. Departments of Internal Medicine, Amstelland Hospital, Amstelveen, The Netherlands. Department of Internal Medicine, Spaarne Hospital, Hoofddorp, The Netherlands. Department of Internal Medicine, Orbis Medical Center, Sittard, The Netherlands. Department of Medical Oncology, Bronovo Hospital, The Hague, The Netherlands. Department of Internal Medicine, Zaans Medical Centre, Zaanstad, The Netherlands. Department of Internal Medicine, Ommelander Hospital, Delfzijl, The Netherlands. Leiden University Medical Center, Department of Medical Decision Making, Leiden, The Netherlands.