[1] Stanford Univ, Dept Med, Div Oncol, Stanford, CA 94305 USA
[2] Stanford Univ, Dept Pathol, Stanford, CA 94305 USA
[3] Univ Calif San Francisco, Dept Radiat Oncol, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, GW Hooper Fdn, San Francisco, CA 94143 USA