[1] Stanford Univ, Sch Med, Dept Radiat Oncol, Palo Alto, CA 94304 USA
[2] Sydney West Radiat Oncol Network, Sydney, NSW, Australia
[3] Univ Sydney, Sydney, NSW, Australia
[4] Stanford Univ, Sch Med, Dept Radiat Oncol, Stanford, CA 94305 USA
[5] Hokkaido Univ, Fac Med, Dept Radiat Med, Sapporo, Hokkaido, Japan
[6] Indiana Univ Sch Med, Dept Radiat Oncol, Indianapolis, IN 46202 USA
[7] Stanford Univ, Sch Med, Dept Med, Stanford, CA 94305 USA