1. School of Medicine, University of California, San Diego, La Jolla
2. Department of Radiation Medicine and Applied Sciences, University of California, San Diego, La Jolla
3. Department of Radiation Oncology, The Johns Hopkins University, Baltimore, Maryland
4. Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon
5. Division of Biostatistics and Bioinformatics, Department of Family Medicine and Public Health, University of California, San Diego, La Jolla
6. Department of Mathematics, University of California, San Diego, La Jolla