[1] Univ Ljubljana, Inst Oncol Ljubljana, Dept Radiat Oncol, Ljubljana 1000, Slovenia
[2] Univ Ljubljana, Fac Med, Ljubljana 1000, Slovenia
[3] Univ Ljubljana, Univ Med Ctr Ljubljana, Dept Otorhinolaryngol & Cervicofacial Surg, Ljubljana 1000, Slovenia
[4] Inst Oncol Ljubljana, Dept Expt Oncol, Izola, Slovenia
[5] Univ Primorska, Fac Hlth Sci, Izola, Slovenia
[6] Univ Ljubljana, Fac Hlth Sci, Ljubljana 1000, Slovenia
[7] Copenhagen Univ Hosp, Rigshosp, Dept Otorhinolaryngol Head & Neck Surg & Audiol, DK-2100 Copenhagen, Denmark
[8] Univ Antwerp, Fac Med & Hlth Sci, Antwerp, Belgium
[9] Antwerp Univ Hosp, Dept Med Oncol, B-2650 Edegem, Belgium
[10] Univ Leuven, KU Leuven, Dept Oncol, B-3000 Leuven, Belgium
[11] UZ Leuven, Dept Radiat Oncol, B-3000 Leuven, Belgium
[12] Univ Utrecht, Univ Med Ctr Utrecht, UMC Utrecht Canc Ctr, Dept Head & Neck Surg Oncol, NL-3584 Utrecht, Netherlands
[13] Univ Michigan, Dept Radiat Oncol, Ann Arbor, MI 48109 USA
[14] Univ Florida, Dept Radiat Oncol, Gainesville, FL 32610 USA
[15] Prince Wales Canc Ctr, Dept Radiat Oncol, Sydney, NSW 2031, Australia
[16] Int Head & Neck Sci Grp, I-35100 Padua, Italy