1. Radiation Oncology Division, European Institute of Oncology, Milan;
2. Department of Medical Physics, Niguarda Hospital, Milan;
3. Department of Senology, European Institute of Oncology, Milan;
4. Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan;
5. Department of Statistics and Modelling Science, Strathclyde University, Glasgow, UK;
6. University of Milan, Italy