1 Division of Biostatistics and Bioinformatics, Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland; Department of Radiation Oncology, University of Maryland Greenebaum Comprehensive Cancer Center, Baltimore, Maryland. Electronic address: sbentzen@som.umaryland.edu.
2 Department of Oncology, Rigshospitalet and Department of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.