1. Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas
2. Division of Biostatistics, Department of Clinical Sciences, University of Texas Southwestern Medical Center, Dallas
3. Department of Statistical Science, Southern Methodist University, Dallas, Texas
4. Department of Radiation Oncology, Brigham and Women’s Hospital, Boston, Massachusetts
5. Dana-Farber Cancer Institute, McGraw/Patterson Center for Population Sciences, Boston, Massachusetts