The analysis set consisted of 739 patients with residues2 .5 cm after chemotherapy from a total of 2,126 patients treated in the HD15 trial ( HD15 for advanced stage Hodgkin 's disease : Quality assurance protocol for reduction of toxicity and the prognostic relevance of fluorodeoxyglucose-positron-emission tomography [ FDG-PET ] in the first-line treatment of advanced-stage Hodgkin 's disease ) performed by the German Hodgkin Study Group .