[1] Leiden Univ, Med Ctr, Dept Surg, NL-2300 RC Leiden, Netherlands
[2] Leiden Univ, Med Ctr, Dept Med Stat, NL-2300 RC Leiden, Netherlands
[3] EORTC Headquarters, Dept Stat, Brussels, Belgium
[4] NKI AVL, Dept Radiotherapy, Amsterdam, Netherlands
[5] Univ Uppsala Hosp, Dept Surg, S-75185 Uppsala, Sweden
[6] Besancon Univ Hosp, Dept Radiat Therapy, Besancon, France
[7] Goethe Univ Frankfurt, Dept Radiat Therapy, Frankfurt, Germany
[8] Muria Sklodowska Curie Mem Canc Ctr, Dept Radiotherapy, Warsaw, Poland