N Gopalakrishna Iyer1,2, Melvin L K Chua3,4. 1. Division of Surgical Oncology, National Cancer Centre, Singapore, Singapore. gopaliyer@nccs.com.sg. 2. Cancer Therapeutics Research Laboratory, National Cancer Centre, Singapore, Singapore. gopaliyer@nccs.com.sg. 3. Division of Radiation Oncology, National Cancer Centre, Singapore, Singapore. melvin.chua.l.k@singhealth.com.sg. 4. Tan Chin Tuan Laboratory of Optical Imaging and Photodynamic and Proton Therapy, National Cancer Centre, Singapore, Singapore. melvin.chua.l.k@singhealth.com.sg.