[1] Vanderbilt Univ, Med Ctr, Nashville, TN USA
[2] Univ Hosp Gasthuisberg, B-3000 Louvain, Belgium
[3] State Univ Ghent Hosp, B-9000 Ghent, Belgium
[4] Univ Calif Los Angeles, Sch Med, Los Angeles, CA USA
[5] Amgen Inc, Biostat, Thousand Oaks, CA USA
[6] Amgen Inc, Oncol Dev, Thousand Oaks, CA USA
[7] Fox Chase Canc Ctr, Philadelphia, PA 19111 USA