1. Division of Therapeutic Radiology and Oncology, Department of Radiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
2. Lampang Cancer Hospital, Lampang, Thailand.
3. Department of Medicine, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
4. Biostatistics and Applied Statistics Laboratory, Department of Statistics, Faculty of Science, Chiang Mai University, Chiang Mai, Thailand.
5. Faculty of Medicine, Christian-Albrechts University at Kiel, Kiel, Germany.