1 Université Laval Cancer Research Centre and CHU de Québec-Université Laval, Quebec City, Quebec, Canada. Electronic address: luc.beaulieu@phy.ulaval.ca.
2 Department of Radiation and Cellular Oncology, University of Chicago, Chicago, Illinois.
3 Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
4 Department of Therapeutic Radiology, Yale University, New Haven, Connecticut.