[1] Univ British Columbia, Dept Med, Vancouver, BC, Canada
[2] Inst Canc Res, Sutton, Surrey, England
[3] Royal Marsden NHS Trust, Sutton, Surrey, England
[4] Univ Calif San Francisco, Dept Neurosurg M787, San Francisco, CA 94143 USA
[5] Univ Texas, MD Anderson Canc Ctr, Dept Neurooncol, Houston, TX 77030 USA