1. Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, New York, USA;
2. Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York, USA;
3. Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York, USA;
4. Department of Radiation Oncology, Mount Sinai Medical Center, New York, New York, USA