1 Department of Medical Oncology, West German Cancer Centre, Ruhrlandklinik, University Hospital Essen, University Duisburg-Essen, 45122 Essen, Germany. Electronic address: wilfried.eberhardt@uni-duisburg-essen.de.
2 Department of Radiation Oncology, West German Tumour Centre, University Hospital Essen, Essen, Germany.