[1] Univ Roma La Sapienza, Div Oncol B, Dept Radiol Oncol & Human Pathol, I-00161 Rome, Italy
[2] Univ Roma La Sapienza, Div Radiotherapy, Dept Radiol Oncol & Human Pathol, I-00161 Rome, Italy
[3] Univ Roma La Sapienza, Div DEA, Dept Surg Sci, I-00161 Rome, Italy
[4] Carnegie Mellon Univ, Pittsburg, KS USA
[5] Univ Roma La Sapienza, Dept Stat Sci, I-00161 Rome, Italy