1. Biostatistics Team; Institut Curie; Paris France
2. Biostatistics Team; Inserm, CESP Center for research in Epidemiology and Population Health, U1018; F-94807 Villejuif France
3. Univ Paris-Sud, UMRS 1018; F-94807 Villejuif France
4. Epidemiology and Clinical Research Department; APHP, Hôpital Louis Mourier; Colombes France