1. Biostatistics Department Institut Gustave‐Roussy Villejuif France
2. INSERM, U717 Biostatistics Department Paris France
3. INSERM, U872, Centre de Recherche des Cordeliers Université Paris 5, Université Paris 6 Paris France
4. Mayo Clinic Rochester, MN U.S.A.
5. Université Paris‐Sud 11 Paris France