[1] Univ Illinois, Dept Med, Hematol Oncol Sect, Chicago, IL 60680 USA
[2] Univ Illinois, Dept Radiat Therapy, Chicago, IL USA
[3] Univ Chicago, Dept Radiat & Cellular Oncol, Chicago, IL 60637 USA
[4] Univ Illinois, Dept Epidemiol Biostat, Chicago, IL USA