Pierre Blanchard1, Yungan Tao2. 1. Gustave Roussy Cancer Campus, Department of Radiation Oncology, Paris Sud University, 94800 Villejuif, France; Meta-analysis Unit, CESP, INSERM 1080, Villejuif, France. Electronic address: pierre.blanchard@gustaveroussy.fr. 2. Gustave Roussy Cancer Campus, Department of Radiation Oncology, Paris Sud University, 94800 Villejuif, France; Molecular Radiation Oncology, INSERM 1030, Villejuif, France.